Bug 1232231 - BorrowDrawTarget can return nullptr - be ready for it. r=nical

--HG--
extra : rebase_source : de5fe177dd405078ba9c370b49b3168a8a51bc29
extra : source : e22122a3bf90033684f1ce762ea29d7e10ae3b93

gfx/layers/TextureWrapperImage.cpp

@@ -40,7 +40,12 @@ TextureWrapperImage::GetAsSourceSurface()
     return nullptr;
   }
 
-  return mTextureClient->BorrowDrawTarget()->Snapshot();
+  RefPtr<DrawTarget> dt = mTextureClient->BorrowDrawTarget();
+  if (!dt) {
+    return nullptr;
+  }
+
+  return dt->Snapshot();
 }
 
 TextureClient*

gfx/layers/client/TextureClient.h

@@ -372,8 +372,14 @@ public:
    */
   already_AddRefed<gfx::DataSourceSurface> GetAsSurface() {
     Lock(OpenMode::OPEN_READ);
-    RefPtr<gfx::SourceSurface> surf = BorrowDrawTarget()->Snapshot();
-    RefPtr<gfx::DataSourceSurface> data = surf->GetDataSurface();
+    RefPtr<gfx::DataSourceSurface> data;
+    RefPtr<gfx::DrawTarget> dt = BorrowDrawTarget();
+    if (dt) {
+      RefPtr<gfx::SourceSurface> surf = dt->Snapshot();
+      if (surf) {
+        data = surf->GetDataSurface();
+      }
+    }
     Unlock();
     return data.forget();
   }