Oilpan: Introduce a dedicated heap for CSSValue and RenderObject

According to our object profiling in micro-benchmarks and real-world benchmarks (https://docs.google.com/a/google.com/spreadsheets/d/1EBYDfkvJ1aleIj0iSNmk0zEsq0AqVOsjEyI6XfOoLIU/edit#gid=562560234), the following objects are allocated very frequently.

- Node
- CSSValue
- RenderObject
- HTMLStackItem
- ElementRecord

Given the results, this CL introduces a dedicated heap for CSSValue and RenderObject. (Note: PartitionAlloc also has a dedicated heap for RenderObject.)

This improves various benchmarks a lot:

css/CSSPropertySetterGetter: +35%
css/ClassInvalidation: +32%
css/StyleSheetInsert: +21%
layout/floats-*: ~+20%
layout/large-table-with-*: ~+10%

BUG=420515

Review URL: https://codereview.chromium.org/667053009

git-svn-id: svn://svn.chromium.org/blink/trunk@184362 bbb929c8-8fbe-4397-9dbb-9b2b20218538

third_party/WebKit/Source/platform/heap/ThreadState.h

@@ -189,7 +189,10 @@ template<typename U> class ThreadingTrait<const U> : public ThreadingTrait<U> {
 // To create a new typed heap add a H(<ClassName>) to the
 // FOR_EACH_TYPED_HEAP macro below.
 #define FOR_EACH_TYPED_HEAP(H)  \
-    H(Node)
+    H(Node) \
+    H(RenderObject) \
+    H(CSSValue)
+
 
 #define TypedHeapEnumName(Type) Type##Heap,
 #define TypedHeapEnumNameNonFinalized(Type) Type##HeapNonFinalized,