cc : Set 'needs update' on transform tree only when something changes

cc/trees/property_tree_unittest.cc

 // Copyright 2014 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "cc/trees/property_tree.h"
 
 #include "cc/input/main_thread_scrolling_reason.h"
 #include "cc/proto/property_tree.pb.h"
 #include "cc/test/geometry_test_utils.h"
 #include "cc/trees/clip_node.h"
@@ skipping 398 matching lines @@
     expected.Translate(-2, -2);
     bool success = tree.CombineInversesBetween(0, 1, &transform);
     EXPECT_TRUE(success);
     EXPECT_TRANSFORMATION_MATRIX_EQ(expected, transform);
   }
 };
 
 DIRECT_AND_SERIALIZED_PROPERTY_TREE_TEST_F(
     PropertyTreeTestComputeTransformRoot);
 
+class PropertyTreeTestSetNeedsUpdate : public PropertyTreeTest {
+ protected:
+  void StartTest() override {
+    PropertyTrees property_trees;
+    TransformTree& tree = property_trees.transform_tree;
+    TransformNode contents_root;
+    contents_root.source_node_id = 0;
+    contents_root.id = tree.Insert(contents_root, 0);
+    tree.SetTargetId(contents_root.id, 0);
+    SetupTransformTreeForTest(&tree);
+
+    EXPECT_FALSE(tree.needs_update());
+    tree.SetRootTransformsAndScales(0.6f, 1.f, gfx::Transform(), gfx::PointF());
+    EXPECT_TRUE(tree.needs_update());
+    tree.set_needs_update(false);
+    tree.SetRootTransformsAndScales(0.6f, 1.f, gfx::Transform(), gfx::PointF());
+    EXPECT_FALSE(tree.needs_update());
+  }
+};
+
+DIRECT_AND_SERIALIZED_PROPERTY_TREE_TEST_F(PropertyTreeTestSetNeedsUpdate);
+
 class PropertyTreeTestComputeTransformChild : public PropertyTreeTest {
  protected:
   void StartTest() override {
     PropertyTrees property_trees;
     TransformTree& tree = property_trees.transform_tree;
     TransformNode contents_root;
     contents_root.local.Translate(2, 2);
     contents_root.source_node_id = 0;
     contents_root.id = tree.Insert(contents_root, 0);
     tree.SetTargetId(contents_root.id, 0);
@@ skipping 589 matching lines @@
 
 DIRECT_AND_SERIALIZED_PROPERTY_TREE_TEST_F(
     PropertyTreeTestSingularTransformSnapTest);
 
 #undef DIRECT_AND_SERIALIZED_PROPERTY_TREE_TEST_F
 #undef SERIALIZED_PROPERTY_TREE_TEST_F
 #undef DIRECT_PROPERTY_TREE_TEST_F
 
 }  // namespace
 }  // namespace cc