Add deferred texture upload API.

src/gpu/GrContext.cpp

Index: src/gpu/GrContext.cpp
diff --git a/src/gpu/GrContext.cpp b/src/gpu/GrContext.cpp
index a16d5c009a8457c2f5d266c342f528cc74181ab6..1f6934d441523d792bf60970bbff7d8cf36645c0 100644
--- a/src/gpu/GrContext.cpp
+++ b/src/gpu/GrContext.cpp
@@ -128,6 +128,13 @@ GrContext::~GrContext() {
     fCaps->unref();
 }
 
+GrContextThreadSafeProxy* GrContext::threadSafeProxy() {
+    if (!fThreadSafeProxy) {
+        fThreadSafeProxy.reset(new GrContextThreadSafeProxy(fCaps, this->uniqueID()));
+    }
+    return SkRef(fThreadSafeProxy.get());
+}
+
 void GrContext::abandonContext() {
     ASSERT_SINGLE_OWNER