Bug 1371956 - Use mApproximatelyVisibleFrames.EnsureInserted/EnsureRemoved to avoid doing unnecessary hashtable lookups. r=froydnj

MozReview-Commit-ID: 87A0v0APtFs

layout/base/PresShell.cpp

@@ -5768,10 +5768,8 @@ PresShell::MarkFramesInListApproximatelyVisible(const nsDisplayList& aList,
 
     // Use the presshell containing the frame.
     auto* presShell = static_cast<PresShell*>(frame->PresContext()->PresShell());
-    uint32_t count = presShell->mApproximatelyVisibleFrames.Count();
     MOZ_ASSERT(!presShell->AssumeAllFramesVisible());
-    presShell->mApproximatelyVisibleFrames.PutEntry(frame);
-    if (presShell->mApproximatelyVisibleFrames.Count() > count) {
+    if (presShell->mApproximatelyVisibleFrames.EnsureInserted(frame)) {
       // The frame was added to mApproximatelyVisibleFrames, so increment its visible count.
       frame->IncApproximateVisibleCount();
     }
@@ -5909,9 +5907,7 @@ PresShell::MarkFramesInSubtreeApproximatelyVisible(nsIFrame* aFrame,
       aFrame->StyleVisibility()->IsVisible() &&
       (!aRemoveOnly || aFrame->GetVisibility() == Visibility::APPROXIMATELY_VISIBLE)) {
     MOZ_ASSERT(!AssumeAllFramesVisible());
-    uint32_t count = mApproximatelyVisibleFrames.Count();
-    mApproximatelyVisibleFrames.PutEntry(aFrame);
-    if (mApproximatelyVisibleFrames.Count() > count) {
+    if (mApproximatelyVisibleFrames.EnsureInserted(aFrame)) {
       // The frame was added to mApproximatelyVisibleFrames, so increment its visible count.
       aFrame->IncApproximateVisibleCount();
     }
@@ -6233,9 +6229,8 @@ PresShell::EnsureFrameInApproximatelyVisibleList(nsIFrame* aFrame)
   }
 #endif
 
-  if (!mApproximatelyVisibleFrames.Contains(aFrame)) {
-    MOZ_ASSERT(!AssumeAllFramesVisible());
-    mApproximatelyVisibleFrames.PutEntry(aFrame);
+  if (mApproximatelyVisibleFrames.EnsureInserted(aFrame)) {
+    // We inserted a new entry.
     aFrame->IncApproximateVisibleCount();
   }
 }
@@ -6258,11 +6253,8 @@ PresShell::RemoveFrameFromApproximatelyVisibleList(nsIFrame* aFrame)
     return;
   }
 
-  uint32_t count = mApproximatelyVisibleFrames.Count();
-  mApproximatelyVisibleFrames.RemoveEntry(aFrame);
-
-  if (aFrame->TrackingVisibility() &&
-      mApproximatelyVisibleFrames.Count() < count) {
+  if (mApproximatelyVisibleFrames.EnsureRemoved(aFrame) &&
+      aFrame->TrackingVisibility()) {
     // aFrame was in the hashtable, and we're still tracking its visibility,
     // so we need to decrement its visible count.
     aFrame->DecApproximateVisibleCount();