cc: Call PrepareTiles when becoming visible in browser only.

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 6d9c9c67199fbe1de37c8e323c741e004d8b6798..f6e5838836df9a8e830052359c7482494afe602f 100644
--- a/cc/trees/layer_tree_host_unittest.cc
+++ b/cc/trees/layer_tree_host_unittest.cc
@@ -231,13 +231,13 @@ class LayerTreeHostTestReadyToDrawEmpty : public LayerTreeHostTest {
   void AfterTest() override {
     EXPECT_TRUE(did_notify_ready_to_draw_);
     EXPECT_TRUE(all_tiles_required_for_draw_are_ready_to_draw_);
-    EXPECT_EQ(size_t(0), required_for_draw_count_);
+    EXPECT_EQ(0, required_for_draw_count_);
   }
 
  protected:
   bool did_notify_ready_to_draw_;
   bool all_tiles_required_for_draw_are_ready_to_draw_;
-  size_t required_for_draw_count_;
+  int required_for_draw_count_;
 };
 
 SINGLE_AND_MULTI_THREAD_TEST_F(LayerTreeHostTestReadyToDrawEmpty);
@@ -261,7 +261,7 @@ class LayerTreeHostTestReadyToDrawNonEmpty
   void AfterTest() override {
     EXPECT_TRUE(did_notify_ready_to_draw_);
     EXPECT_TRUE(all_tiles_required_for_draw_are_ready_to_draw_);
-    EXPECT_LE(size_t(1), required_for_draw_count_);
+    EXPECT_LE(1, required_for_draw_count_);
   }
 
  private:
@@ -272,6 +272,32 @@ class LayerTreeHostTestReadyToDrawNonEmpty
 // single threaded mode.
 SINGLE_THREAD_TEST_F(LayerTreeHostTestReadyToDrawNonEmpty);
 
+class LayerTreeHostTestReadyToDrawVisibility

[brianderson, 2015/07/16 22:36:14]

Can you add a comment explaining what this test does an why. 

[sunnyps, 2015/07/16 22:51:44]

Done.

+    : public LayerTreeHostTestReadyToDrawNonEmpty {
+ public:
+  LayerTreeHostTestReadyToDrawVisibility()
+      : LayerTreeHostTestReadyToDrawNonEmpty(), did_commit_(false) {}
+
+  void CommitCompleteOnThread(LayerTreeHostImpl* host_impl) override {
+    EXPECT_FALSE(did_commit_);
+    did_commit_ = true;
+    PostSetVisibleToMainThread(false);
+  }
+
+  void DidSetVisibleOnImplTree(LayerTreeHostImpl* host_impl,
+                               bool visible) override {
+    if (!visible) {
+      EXPECT_TRUE(did_commit_);
+      PostSetVisibleToMainThread(true);

[brianderson, 2015/07/16 22:36:14]

To test the test, could you:
DCHECK(!all_tiles_required_for_draw_are_ready_to_draw_)
here?

[sunnyps, 2015/07/16 22:51:44]

Done.

+    }
+  }
+
+ protected:
+  bool did_commit_;
+};
+
+SINGLE_THREAD_TEST_F(LayerTreeHostTestReadyToDrawVisibility);
+
 class LayerTreeHostFreeWorkerContextResourcesTest : public LayerTreeHostTest {
  public:
   scoped_ptr<FakeOutputSurface> CreateFakeOutputSurface() override {