compositor-worker: Introduce WebCompositorMutableState

cc/animation/layer_tree_mutation.h

Index: cc/animation/layer_tree_mutation.h
diff --git a/cc/animation/layer_tree_mutation.h b/cc/animation/layer_tree_mutation.h
new file mode 100644
index 0000000000000000000000000000000000000000..9b745ae02843f168baaa9ddb4f4628ab3f51c696
--- /dev/null
+++ b/cc/animation/layer_tree_mutation.h
@@ -0,0 +1,63 @@
+// Copyright 2015 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.
+
+#ifndef CC_ANIMATION_LAYER_TREE_MUTATION_H_
+#define CC_ANIMATION_LAYER_TREE_MUTATION_H_
+
+#include "base/containers/hash_tables.h"
+#include "cc/animation/mutable_properties.h"
+#include "third_party/skia/include/utils/SkMatrix44.h"
+
+namespace cc {
+
+struct LayerTreeMutation {

[esprehn, 2016/01/06 19:48:37]

class ? You have public: and all the state is private

[Ian Vollick, 2016/01/08 03:01:53]

Done.

+ public:
+  void SetOpacity(float opacity) {
+    mutated_flags_ |= kMutablePropertyOpacity;
+    opacity_ = opacity;
+  }
+  void SetScrollLeft(float scroll_left) {
+    mutated_flags_ |= kMutablePropertyScrollLeft;
+    scroll_left_ = scroll_left;
+  }
+  void SetScrollTop(float scroll_top) {
+    mutated_flags_ |= kMutablePropertyScrollTop;
+    scroll_top_ = scroll_top;
+  }
+  void SetTransform(const SkMatrix44& transform) {
+    mutated_flags_ |= kMutablePropertyTransform;
+    transform_ = transform;
+  }
+
+  bool is_opacity_mutated() const {
+    return !!(mutated_flags_ & kMutablePropertyOpacity);
+  }
+  bool is_scroll_left_mutated() const {
+    return !!(mutated_flags_ & kMutablePropertyScrollLeft);
+  }
+  bool is_scroll_top_mutated() const {
+    return !!(mutated_flags_ & kMutablePropertyScrollTop);
+  }
+  bool is_transform_mutated() const {
+    return !!(mutated_flags_ & kMutablePropertyTransform);
+  }
+
+  float opacity() const { return opacity_; }
+  float scroll_left() const { return scroll_left_; }
+  float scroll_top() const { return scroll_top_; }
+  SkMatrix44 transform() const { return transform_; }
+
+ private:
+  uint32_t mutated_flags_ = 0;
+  float opacity_ = 0;
+  float scroll_left_ = 0;
+  float scroll_top_ = 0;
+  SkMatrix44 transform_;
+};
+
+typedef base::hash_map<uint64_t, LayerTreeMutation> LayerTreeMutationMap;

[esprehn, 2016/01/06 19:48:37]

note that LayerTreeMutation objects are pretty big, so the map is wasting a
bunch of space. We usually do put OwnPtr<T> into the map instead. I guess this
map isn't usually very large?

[Ian Vollick, 2016/01/08 03:01:53]

That's true. You could have one of these for every compositor proxy you muck
with in a frame, so it's probably not usually very large, but it could be. That
said, the plan is to copy this as little as possible -- we'll make a copy to
send values back to the main thread, eg.

+
+}  // namespace cc
+
+#endif  // CC_ANIMATION_LAYER_TREE_MUTATION_H_