Free cached AA clip mask when create hard/stencil clip mask

http://codereview.appspot.com/6214050/



git-svn-id: http://skia.googlecode.com/svn/trunk@3983 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 5ec6511..bd6d829 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -67,6 +67,11 @@
 
 GrContext::~GrContext() {
     this->flush();
+
+    // Since the gpu can hold scratch textures, give it a chance to let go
+    // of them before freeing the texture cache
+    fGpu->purgeResources();
+
     delete fTextureCache;
     delete fFontCache;
     delete fDrawBuffer;