Bug 1376640. Fix dynamic updates when an inline that sits between a first-letter and its block changes style. r=heycam

MozReview-Commit-ID: 8osMUpYVRvR

layout/base/nsCSSFrameConstructor.cpp

@@ -11811,6 +11811,8 @@ nsCSSFrameConstructor::CreateLetterFrame(nsContainerFrame* aBlockFrame,
     }
     MOZ_ASSERT(!aBlockFrame->GetPrevContinuation(),
                "Setting up a first-letter frame on a non-first block continuation?");
+    auto parent = static_cast<nsContainerFrame*>(aParentFrame->FirstContinuation());
+    parent->SetHasFirstLetterChild();
     aBlockFrame->SetProperty(nsContainerFrame::FirstLetterProperty(),
                              letterFrame);
     aTextContent->SetPrimaryFrame(textFrame);
@@ -11956,6 +11958,8 @@ nsCSSFrameConstructor::RemoveFloatingFirstLetterFrames(
     // Somethings really wrong
     return;
   }
+  static_cast<nsContainerFrame*>(parentFrame->FirstContinuation())->
+    ClearHasFirstLetterChild();
 
   // Create a new text frame with the right style context that maps
   // all of the content that was previously part of the letter frame
@@ -12021,6 +12025,8 @@ nsCSSFrameConstructor::RemoveFirstLetterFrames(nsIPresShell* aPresShell,
   while (kid) {
     if (kid->IsLetterFrame()) {
       // Bingo. Found it. First steal away the text frame.
+      static_cast<nsContainerFrame*>(aFrame->FirstContinuation())->
+        ClearHasFirstLetterChild();
       nsIFrame* textFrame = kid->PrincipalChildList().FirstChild();
       if (!textFrame) {
         break;