Implemented prototype for new ink drop specs.

chrome/browser/ui/views/toolbar/back_button.cc

Index: chrome/browser/ui/views/toolbar/back_button.cc
diff --git a/chrome/browser/ui/views/toolbar/back_button.cc b/chrome/browser/ui/views/toolbar/back_button.cc
index 73ae0411c64c06f374cbaab0be52536da6b57451..630c1fff5147b27f903b85b67c37249bb12487fb 100644
--- a/chrome/browser/ui/views/toolbar/back_button.cc
+++ b/chrome/browser/ui/views/toolbar/back_button.cc
@@ -33,8 +33,12 @@ void BackButton::SetLeadingMargin(int margin) {
 }
 
 void BackButton::LayoutInkDrop() {
-  ink_drop_animation_controller()->SetInkDropBounds(
-      gfx::Rect(margin_leading_, 0, width() - margin_leading_, height()));
+  ToolbarButton::LayoutInkDrop();
+  gfx::Size ink_drop_size =
+      ink_drop_animation_controller()->GetInkDropLargeSize();
+  ink_drop_animation_controller()->SetInkDropOrigin(gfx::Point(
+      margin_leading_ + (width() - margin_leading_ - ink_drop_size.width()) / 2,
+      (height() - ink_drop_size.height()) / 2));
 }
 
 const char* BackButton::GetClassName() const {