Oilpan: promptly free per-frame document heap vector.

Source/core/page/PageAnimator.cpp

Index: Source/core/page/PageAnimator.cpp
diff --git a/Source/core/page/PageAnimator.cpp b/Source/core/page/PageAnimator.cpp
index 752a59083ebcc77be2d3963acbd1ce0721dea99d..33b601b732a9837cf713c3dfc12f228f4a4ef253 100644
--- a/Source/core/page/PageAnimator.cpp
+++ b/Source/core/page/PageAnimator.cpp
@@ -68,6 +68,10 @@ void PageAnimator::serviceScriptedAnimations(double monotonicAnimationStartTime)
 
     for (size_t i = 0; i < documents.size(); ++i)
         documents[i]->serviceScriptedAnimations(monotonicAnimationStartTime);
+
+#if ENABLE(OILPAN)
+    documents.clear();

[dstockwell, 2015/03/10 22:38:31]

This might be a reasonable optimiziation, but to a non-oilpan expert it's not
clear what the purpose is. Once the oilpan if-defs are removed there's nothing
to prevent someone from cleaning this up. Is there something we can do to
improve the readability here? Maybe a different named HeapVector?

[haraken, 2015/03/10 23:26:08]

Yeah, that's something we're considering.

Option 1: Introduce StackVector.

Option 2: Add a destructor for an on-stack HeapVector so that the HeapVector is
promptly cleared. (But I'm failing at implementing the destructor in a way in
which it doesn't regress performance.)

Option 3: Explicitly add .clear() with a comment.

+#endif
 }
 
 void PageAnimator::scheduleVisualUpdate(LocalFrame* frame)