Introduce bottom controls to CC and let it respond to scrolling

cc/input/top_controls_manager.cc

Index: cc/input/top_controls_manager.cc
diff --git a/cc/input/top_controls_manager.cc b/cc/input/top_controls_manager.cc
index 2b7b55b3c5de69a840d52f84b2fa3029d27565a8..c9d5c705ca6c85911bc598576fe3803dd7842922 100644
--- a/cc/input/top_controls_manager.cc
+++ b/cc/input/top_controls_manager.cc
@@ -68,6 +68,18 @@ float TopControlsManager::TopControlsHeight() const {
   return client_->TopControlsHeight();
 }
 
+float TopControlsManager::BottomControlsHeight() const {
+  return client_->BottomControlsHeight();
+}
+
+float TopControlsManager::BottomControlsOffset() const {
+  return TopControlsShownRatio() * BottomControlsHeight();
+}
+
+float TopControlsManager::BottomContentOffset() const {
+  return BottomControlsHeight() - BottomControlsOffset();

[bokan, 2016/06/30 12:31:21]

This feels odd to me. When shown ratio is 0, BottomContentOffset will be
BottomControlsHeight. What does this method actually represent?

[Ian Wen, 2016/07/01 02:51:44]

Hmmm you are right. I should swap the value content-offset and controls-offset
here.

content-offset should mean "how much this bar takes on the screen now", and
controls-offset means "how much should I translate this bar". Actually I renamed
the values in the IPC message and browser side so that they make more sense.

+}
+
 void TopControlsManager::UpdateTopControlsState(TopControlsState constraints,
                                                 TopControlsState current,
                                                 bool animate) {