Introduce bottom controls to CC and let it respond to scrolling

content/common/resize_params.cc

Index: content/common/resize_params.cc
diff --git a/content/common/resize_params.cc b/content/common/resize_params.cc
index ea9f18fb65b2041e7fda33666b7a6dbbd496b4af..ee6943fc77b95ee5f54e343af57aea69f087c77f 100644
--- a/content/common/resize_params.cc
+++ b/content/common/resize_params.cc
@@ -9,6 +9,7 @@ namespace content {
 ResizeParams::ResizeParams()
     : top_controls_shrink_blink_size(false),
       top_controls_height(0.f),
+      bottom_controls_height(0.f),
       is_fullscreen_granted(false),
       display_mode(blink::WebDisplayModeUndefined),
       needs_resize_ack(false) {}