Bug 1283222 - Do not record soft break opportunities for out-of-flow frames. r=emilio

We do want to record soft break opportunity after a frame whose content can't
be part of the existing in-flow text run, since this normally should be a text run
boundary. However, though an out-of-flow frame can't be part of the existing
in-flow text run, it also doesn't break it either. In fact, the texts after the
out-of-flow frames are able to continue the existing in-flow text run. So,
introducing a line-break-after opportunity in this case may cause an unexpected
line break for every out-of-flow frame.

In this patch, we add a condition to prevent us from recording soft break
opportunities for out-of-flow frames.

Differential Revision: https://phabricator.services.mozilla.com/D28625

--HG--
extra : moz-landing-system : lando

layout/generic/nsLineLayout.cpp

@@ -890,7 +890,6 @@ void nsLineLayout::ReflowFrame(nsIFrame* aFrame, nsReflowStatus& aReflowStatus,
   // See if the frame is a placeholderFrame and if it is process
   // the float. At the same time, check if the frame has any non-collapsed-away
   // content.
-  bool placedFloat = false;
   bool isEmpty;
   if (frameType == LayoutFrameType::None) {
     isEmpty = pfd->mFrame->IsEmpty();
@@ -918,7 +917,7 @@ void nsLineLayout::ReflowFrame(nsIFrame* aFrame, nsReflowStatus& aReflowStatus,
           // We'll do this at the next break opportunity.
           RecordNoWrapFloat(outOfFlowFrame);
         } else {
-          placedFloat = TryToPlaceFloat(outOfFlowFrame);
+          TryToPlaceFloat(outOfFlowFrame);
         }
       }
     } else if (isText) {
@@ -1064,11 +1063,12 @@ void nsLineLayout::ReflowFrame(nsIFrame* aFrame, nsReflowStatus& aReflowStatus,
       }
 
       if (!continuingTextRun && !psd->mNoWrap) {
-        if (!LineIsEmpty() || placedFloat) {
+        if (!LineIsEmpty()) {
           // record soft break opportunity after this content that can't be
           // part of a text run. This is not a text frame so we know
           // that offset INT32_MAX means "after the content".
-          if (NotifyOptionalBreakPosition(aFrame, INT32_MAX,
+          if (!aFrame->IsPlaceholderFrame() &&
+              NotifyOptionalBreakPosition(aFrame, INT32_MAX,
                                           optionalBreakAfterFits,
                                           gfxBreakPriority::eNormalBreak)) {
             // If this returns true then we are being told to actually break

testing/web-platform/meta/css/css-text/line-breaking/line-breaking-016.html.ini

@@ -1,3 +0,0 @@
-[line-breaking-016.html]
-  expected:
-    FAIL

testing/web-platform/meta/css/css-text/line-breaking/line-breaking-017.html.ini

@@ -1,3 +0,0 @@
-[line-breaking-017.html]
-  expected:
-    FAIL