Add mechanism to proactively purge old resources in GrResourceCache.

src/gpu/GrContext.cpp

Index: src/gpu/GrContext.cpp
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index b38bc1eea83c1656de881be601dc04e12d702d5c..134d8b906c6905c57b35db26de95341ddf7d5e49 100755
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -1474,6 +1474,7 @@ void GrContext::flush(int flagsBitfield) {
     } else {
         fDrawBuffer->flush();
     }
+    fResourceCache->notifyFlushOccurred();
     fFlushToReduceCacheSize = false;
 }