Introduce painted-device-scale-factor and use it when --enable-use-zoom-for-dsf is specified.

cc/trees/layer_tree_host_unittest.cc

Index: cc/trees/layer_tree_host_unittest.cc
diff --git a/cc/trees/layer_tree_host_unittest.cc b/cc/trees/layer_tree_host_unittest.cc
index e75b3e9a2ba4a0324fee2176942bc83c2080f5a7..1c7c270bb1d7635e1be089cdd75adcde98acc86e 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -6378,5 +6378,43 @@ class LayerTreeHostTestDestroyWhileInitializingOutputSurface
 
 MULTI_THREAD_TEST_F(LayerTreeHostTestDestroyWhileInitializingOutputSurface);
 
+class LayerTreeHostTestPaintedDeviceScaleFactor : public LayerTreeHostTest {

[oshima, 2015/10/22 21:47:42]

danakj@, I'm not sure if this is right place, way , enough to test. Let me know
if you have any advice.

+  class PaintedScaleSwapPromise : public SwapPromise {
+   public:
+    PaintedScaleSwapPromise() {}
+    ~PaintedScaleSwapPromise() override {}
+    void DidActivate() override {}
+    void DidSwap(CompositorFrameMetadata* metadata) override {
+      EXPECT_EQ(2.0f, metadata->device_scale_factor);
+    }
+    void DidNotSwap(DidNotSwapReason reason) override {}
+    int64 TraceId() const override { return 0; }
+  };
+
+ protected:
+  void BeginTest() override {
+    layer_tree_host()->SetPaintedDeviceScaleFactor(2.0f);
+    ASSERT_EQ(1.0f, layer_tree_host()->device_scale_factor());

[danakj, 2015/10/22 23:15:29]

EXPECT_EQ

[oshima, 2015/10/23 18:05:36]

Done.

+    PostSetNextCommitForcesRedrawToMainThread();

[danakj, 2015/10/22 23:15:29]

not needed, we'll draw the first frame

[oshima, 2015/10/23 18:05:36]

Done.

+    PostSetNeedsCommitToMainThread();
+  }
+
+  void CommitCompleteOnThread(LayerTreeHostImpl* host_impl) override {
+    int frame = host_impl->active_tree()->source_frame_number();
+    if (frame == -1) {
+      host_impl->active_tree()->QueuePinnedSwapPromise(
+          make_scoped_ptr(new PaintedScaleSwapPromise()));
+    }
+  }
+
+  void SwapBuffersOnThread(LayerTreeHostImpl* host_impl, bool result) override {

[danakj, 2015/10/22 23:15:29]

Can you just use
https://code.google.com/p/chromium/codesearch#chromium/src/cc/test/fake_outpu...
to check this instead of a swap promise?

[oshima, 2015/10/23 18:05:36]

Thanks, I'll look into it.

[oshima, 2015/10/23 22:05:02]

Actually I could just check the last frame here. Let me know if this is ok.

+    EndTest();
+  }
+
+  void AfterTest() override {}
+};
+
+MULTI_THREAD_TEST_F(LayerTreeHostTestPaintedDeviceScaleFactor);
+
 }  // namespace
 }  // namespace cc