Attached ClipMaskManager to GPU resource freeing system

http://codereview.appspot.com/6208058/



git-svn-id: http://skia.googlecode.com/svn/trunk@3927 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index 8d5b88f..aaf2ae4 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -110,6 +110,9 @@
 
 void GrContext::freeGpuResources() {
     this->flush();
+    
+    fGpu->purgeResources();
+
     fTextureCache->removeAll();
     fFontCache->freeAll();
     // a path renderer may be holding onto resources