Support for WITH_JSC_MEMORY_PRESSURE in iOS 8's JSC.

Reviewed By: lexs

Differential Revision: D3162471

fb-gh-sync-id: 1fb1584ccfa507c5697958ce8837f637fa8a301c
fbshipit-source-id: 1fb1584ccfa507c5697958ce8837f637fa8a301c

ReactAndroid/src/main/jni/react/BUCK

@@ -14,7 +14,7 @@ PREPROCESSOR_FLAGS = [
   '-DLOG_TAG="ReactNative"',
   '-DWITH_JSC_EXTRA_TRACING=1',
   '-DWITH_FBSYSTRACE=1',
-  # '-DWITH_JSC_MEMORY_PRESSURE=1', # Taken care of in D3162471
+  '-DWITH_JSC_MEMORY_PRESSURE=1',
   # '-DWITH_JSC_INTERNAL=1',  # Taken care of in D3163295
 ]