Use PartitionAlloc for fastMalloc on Android

This switches fastMalloc to PartitionAlloc for Android. Previously, we only
used PartitionAlloc for fastMalloc on Mac OS X.

According to primiano's measurements, this CL should improve PLT performance
on Android by 7%.  See referenced bug for details.

alexa_us on N10 with default alloc (without
#     ms/page  PSS   Dirty
#1    227.6   60410 44904
#2    226.1   61547 46008
#3    222.4   55595 40072
#4    224.2   57293 41728
AVG   225.1   58711 43178

alexa_us on N10 with partalloc
#     ms/page  PSS   Dirty
#1    204.68  54862  39456
#2    208.73  59240  43844
#3    208.57  55164  39788
#4    217.28  58280  42904
AVG   209.81  56886  41498

BUG=312725
[email protected]

Review URL: https://codereview.chromium.org/148013010

git-svn-id: svn://svn.chromium.org/blink/trunk@166271 bbb929c8-8fbe-4397-9dbb-9b2b20218538

Source/config.h

@@ -98,14 +98,13 @@
 #if OS(MACOSX)
 #define WTF_USE_CF 1
 #define WTF_USE_RUBBER_BANDING 1
+#endif /* OS(MACOSX) */
 
-/* We can't override the global operator new and delete on OS(MACOSX) because
- * some object are allocated by WebKit and deallocated by the embedder. */
-#else /* !OS(MACOSX) */
-/* On non-OS(MACOSX), the "system malloc" is actually TCMalloc anyway, so there's
+#if !OS(MACOSX) && !OS(ANDROID)
+/* On other platforms the "system malloc" is TCMalloc, so there's
  * no need to use Blink's fast PartitionAlloc allocator. */
 #define WTF_USE_SYSTEM_MALLOC 1
-#endif /* OS(MACOSX) */
+#endif /* !OS(MACOSX) && !OS(ANDROID) */
 
 #if OS(POSIX)
 #define HAVE_MMAP 1