Revert of Use presence of a content key as non-scratch indicator

src/gpu/GrGpuResource.cpp

Index: src/gpu/GrGpuResource.cpp
diff --git a/src/gpu/GrGpuResource.cpp b/src/gpu/GrGpuResource.cpp
index 5452184793eab9c01f98f3ed1cf907d1b7203897..a074d7c29e0bbffd09dac65b75b6957cbf9e66e9 100644
--- a/src/gpu/GrGpuResource.cpp
+++ b/src/gpu/GrGpuResource.cpp
@@ -101,13 +101,6 @@
     fScratchKey = scratchKey;
 }
 
-const GrResourceKey* GrGpuResource::getContentKey() const {
-    if (fCacheEntry && !fCacheEntry->key().isScratch()) {
-        return &fCacheEntry->key();
-    }
-    return NULL;
-}
-
 uint32_t GrGpuResource::CreateUniqueID() {
     static int32_t gUniqueID = SK_InvalidUniqueID;
     uint32_t id;