Return overscroll data from cc::InputHandler::ScrollBy

Whether or not a cc::InputHandler::ScrollBy resulted in some scrolling
happening is returned as a bool from the function, but whether or not
all of the input scroll delta was used is made available through a callback
to the cc::InputHandlerClient::DidOverscroll function. All of this information
should be made available in the return value.

Make ScrollBy return a struct that contains information about if a scroll
happened, if an overscroll happened, and how much of an overscroll
happened.

The overscroll effect on Mac will require knowledge of exactly what
happened with scroll (was there any extra overscroll, etc) at the point
where the scroll is attempted.

BUG=133097

Review URL: https://codereview.chromium.org/701343002

Cr-Commit-Position: refs/heads/master@{#303172}

1 files changed, 13 insertions, 0 deletions

diff --git a/cc/input/input_handler.cc b/cc/input/input_handler.cc
new file mode 100644
index 0000000..336d0d4
--- /dev/null
+++ b/cc/input/input_handler.cc
@@ -0,0 +1,13 @@
+// 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/input/input_handler.h"
+
+namespace cc {
+
+InputHandlerScrollResult::InputHandlerScrollResult()
+    : did_scroll(false), did_overscroll_root(false) {
+}
+
+}  // namespace cc