Makes it easier to snap or dock windows near the edges when using touch

ash/wm/workspace/snap_sizer.cc

 // Copyright (c) 2012 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 "ash/wm/workspace/snap_sizer.h"
 
 #include <cmath>
 
 #include "ash/ash_switches.h"
 #include "ash/screen_util.h"
@@ skipping 116 matching lines @@
                         const gfx::Rect& snap_bounds) {
   if (edge == SnapSizer::LEFT_EDGE) {
     window_state->SnapLeft(snap_bounds);
   } else {
     window_state->SnapRight(snap_bounds);
   }
 }
 
 }  // namespace
 
+// static
+const int SnapSizer::kScreenEdgeInsetForTouchDrag = 32;
+
 SnapSizer::SnapSizer(wm::WindowState* window_state,
                      const gfx::Point& start,
                      Edge edge,
                      InputType input_type)
     : window_state_(window_state),
       edge_(edge),
       time_last_update_(base::TimeTicks::Now()),
       size_index_(0),
       end_of_sequence_(false),
       resize_disabled_(false),
@@ skipping 131 matching lines @@
   last_adjust_x_ = x;
 }
 
 gfx::Rect SnapSizer::GetTargetBounds() const {
   return GetTargetBoundsForSize(size_index_);
 }
 
 bool SnapSizer::AlongEdge(int x) const {
   gfx::Rect area(ScreenUtil::GetDisplayWorkAreaBoundsInParent(
       window_state_->window()));
-  return (x <= area.x()) || (x >= area.right() - 1);
+  int inset =
+      input_type_ == TOUCH_DRAG_INPUT ? kScreenEdgeInsetForTouchDrag : 0;
+  return (x <= area.x() + inset) || (x >= area.right() - 1 - inset);
 }
 
 }  // namespace internal
 }  // namespace ash