import changes from `dev' branch of rmottola/Arctic-Fox:

- Bug 1161049 patch 2 - Add comments reflecting what CanPerformOnCompositorThread doesn't check. r=birtles (09854c55c)
- Bug 1161049 patch 3 - Don't send animations to a layer if we're not using off-main-thread compositing. r=mstange (927242bde)
- Bug 1148418 - Make nsDisplayBackgroundColor::Paint use a higher precision floating point type to avoid scrolling artifacts. r=mattwoodrow (3641d43be)
- Bug 1148418 - Follow-up to avoid unused variable warning. r=bustage CLOSED TREE (83d4dd8fe)
- Bug 804975 - Part 2: Add a RuleNodeCacheConditions class and use it instead of a boolean canStoreInRuleTree during style computation. r=dbaron (fce3718c4)
- Bug 804975 - Part 3: Support conditional cached reset structs on rule nodes. r=dbaron (a2a049f56)
- Bug 804975 - Part 4: Cache reset structs on rule nodes for different font-size or writing mode values. r=dbaron (9bac1c6db)
- Bug 77999 - Unified build fix followup. (a2c95b3b4)
- Bug 1169440 patch 1 - Add bitwise operators to nsChangeHint. r=heycam (d30d0a0a2)
- Bug 1169440 patch 2 - Rename style struct MaxDifferenceNeverInherited to DifferenceAlwaysHandledForDescendants. r=heycam (7d1e2cdae)
- Bug 1156988 - Update RestyleManager::{Change,Restyle}HintToString for recent changes. r=dbaron (547e61dd6)
- Bug 1169440 patch 3 - Add nsChangeHint_ReflowChangesSizeOrPosition. r=heycam (0076ee033)
- Bug 1177076 patch 1 - Add logical values for the caption-side property (though not yet handled by layout code). r=heycam (4e8bd065d)
- Bug 1131000. Implement nsMathMLSelectedFrame::ComputeSize to delegate size computation to the selected frame. r=mats (49581cdd7)
- Bug 1172774: for a box with a writing mode orthogonal to its containing block, calculate positioning values (margin, padding and offsets) in the writing mode of the containing block, r=jfkthame (505cd7afb)
- Bug 1177076 patch 2 - Convert nsTableOuterFrame to work with logical coordinates. r=dholbert (300c5cfae)
- Bug 1151993 - Reftest for inline-sizing of orthogonal block frames. r=smontagu (c17e188b1)
- Bug 1144501 - Reftest for sizing of orthogonal frame after block-end margin. r=smontagu (d27d90068)
- Bug 1156021 - Reftest for text-indent specified as percent in vertical writing mode. r=dbaron (d25854ee0)
- Bug 1158549 - Reftest for size constraints in vertical writing mode. r=smontagu (b1d7f74aa)
- Bug 1157752 - Reftest for vertical mode with upright orientation overriding bidi directionality. r=smontagu (b7aedaf06)
- Bug 1152941 - Reftest for orthogonal block with potentially overflowing content. r=dbaron (0fe1d83f4)
- Bug 1077521 - Initial testcases for vertical writing-mode tables. r=smontagu (dbacaf74c)
- Bug 1077521 - Reftest for rowspan in vertical table. r=smontagu (e4b6134bf)
- Bug 1077521 - Reftest for colspan in vertical table. r=smontagu (ece444c32)
- Bug 1177606 - Reftests for vertical tables with specified width. (d7f9ddc3a)
- Bug 1157569 - Reftests for vertical-mode table with border-collapse. r=dholbert (0b9b7eeae)
- Tests for bug 1173958. r=jfkthame (64278818c)
- Bug 1139306: Add a small amount of fuzz to a test on Android, r=tn (b879499c6)
- Bug 1140160 - Handle insertions into a <fieldset> child with display:contents correctly. r=roc (39a24c684)
- partial 1138442 (3d04520fd)
- Bug 1153757 - Tweak DoGetParentStyleContext to exclude pseudos with a non-primary frame from using a display:contents parent as the style context parent. r=heycam (caa35c9ac)
- part of 1144080 (465618308)
- reapply 932958 (f098ad575)
- part of 1153574 (8e4532dc5)
- Bug 1169331 - Always clip rotated buffer quadrant drawing to the fill rect. r=jrmuizel (4693f9c1c)
- Bug 1174332 - Correctly compute box-shadow bounds on themed frames with overflow. r=roc (489b069a5)
- Bug 1169525 - Add the on-demand SVG style sheets when a foreignObjectis encountered within a single style update. r=jwatt (ebe0eb228)
- Bug 1169514 - Part 1: Move noscript rule from the preference style sheet to a cached UA style sheet. r=jwatt (a04979f0f)
- Bug 1169514 - Part 2: Move noframes rules from the preferences style sheet to a cached UA style sheet. r=jwatt (26aae1a45)
- Bug 1174450 part 1 - Split IntrinsicForContainer in two parts; move the latter part to a new function, AddIntrinsicSizeOffset, which applies the padding/border/margin from the given IntrinsicISizeOffsetData. r=jfkthame (37202f0f3)
- Bug 1174450 part 2 - Rename most AddIntrinsicSizeOffset params to follow the aName standard. r=jfkthame (4525fa9c5)
- Bug 1174450 part 3 - Rename AddIntrinsicSizeOffset local vars from xISize to xSize since the code is generic and handles both ISizes and BSizes. r=jfkthame (6a4816b18)
- Bug 1174450 part 4 - Rename the remaining AddIntrinsicSizeOffset params to follow the aName standard. Also rename local var 'w' to 'size' since it may be either a width or height. r=jfkthame (e1132b475)
- Bug 1174450 part 5 - Remove the duplicated min/max calculation in AddIntrinsicSizeOffset, pass a pointer to the calculated absolute values, if any, from IntrinsicForContainer instead. r=jfkthame (85f937449)
- Bug 1174450 part 6 - Add a doc comment for AddIntrinsicSizeOffset and some minor code style fixes. r=jfkthame (1e501c748)
- Bug 1174450 part 7 - Move most of IntrinsicForContainer into a new method, IntrinsicForWM, that takes the writing-mode to use as a parameter. r=jfkthame (db3ba1bc4)
- Bug 1174450 part 8 - Add a new method nsIFrame::IntrinsicBSizeOffsets. r=jfkthame (ef1715d4e)
- Bug 1174450 part 9 - Remove the nsRenderingContext* param from Intrinsic*SizeOffsets methods since it's unused. r=jfkthame (e0fd79cc6)
- Bug 1174450 part 10 - Use the right IntrinsicISizeOffsetData for the given writing-mode (this is what fixes the error reported in this bug). r=jfkthame (efc490611)
- Bug 1174450 part 9b - Make AddIntrinsicSizeOffset take a PhysicalAxis instead of a WritingMode. r=jfkthame (cab48ffef)
- Bug 1174450 part 10b - Rename IntrinsicForWM to IntrinsicForAxis and make it take a PhysicalAxis instead of a WritingMode. r=jfkthame (cd33baeff)
- Bug 1147834: tests for overconstrained relative positioning, r=jfkthame (c2c67b2fc)
- Bug 1157758 - Reftest for Arabic text in vertical-upright mode. r=jdaggett (689b0a84d)
- Bug 1163238 - Reftest for auto margins on orthogonal flow. (c9f5a50ec)
- Bug 1079151 - Tests for position:absolute in vertical writing modes; currently failing 72 out of 96 testcases. r=jfkthame (228756de5)
- Tests for bug 1172774, r=jfkthame (91ff7737d)
- Bug 1174450 part 11 - Tests. (89963b6a7)
- convert file to UTF-8 (f8e2e497a)

layout/base/nsCSSFrameConstructor.cpp

@@ -6702,7 +6702,12 @@ nsCSSFrameConstructor::GetInsertionPrevSibling(InsertionPoint* aInsertion,
         // the container would be inserted.  This is needed when inserting
         // into nested display:contents nodes.
         nsIContent* child = aInsertion->mContainer;
-        InsertionPoint fakeInsertion(aInsertion->mParentFrame, child->GetParent());
+        nsIContent* parent = child->GetParent();
+        aInsertion->mParentFrame =
+          ::GetAdjustedParentFrame(aInsertion->mParentFrame,
+                                   aInsertion->mParentFrame->GetType(),
+                                   parent);
+        InsertionPoint fakeInsertion(aInsertion->mParentFrame, parent);
         nsIFrame* result = GetInsertionPrevSibling(&fakeInsertion, child, aIsAppend,
                                                    aIsRangeInsertSafe, nullptr, nullptr);
         MOZ_ASSERT(aInsertion->mParentFrame->GetContent() ==
@@ -9079,8 +9084,10 @@ nsCSSFrameConstructor::GetInsertionPoint(nsIContent* aContainer,
   InsertionPoint insertion(GetContentInsertionFrameFor(insertionElement),
                            insertionElement);
 
-  // Fieldsets have multiple insertion points.
-  if (insertionElement->IsHTMLElement(nsGkAtoms::fieldset)) {
+  // Fieldset frames have multiple normal flow child frame lists so handle it
+  // the same as if it had multiple content insertion points.
+  if (insertion.mParentFrame &&
+      insertion.mParentFrame->GetType() == nsGkAtoms::fieldSetFrame) {
     insertion.mMultiple = true;
   }