Reland: Aura: Fix crash on dragging URL into tab strip

The widget for the window containing the drop-location arrow needs a parent
under Aura to be placed correctly. A parent or context for each widget is
required due to https://codereview.chromium.org/11829040/

BUG=173229
TEST=Open two tabs, verify you can drag a blue URL link into the space between the two tabs in the tab strip. The URL should open in a new tab and Chrome should not crash.
TBR=sky@chromium.org

Original commit: https://src.chromium.org/viewvc/chrome?view=rev&revision=180006

Review URL: https://codereview.chromium.org/12096103

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@180151 0039d316-1c4b-4281-b951-d872f2087c98

chrome/browser/ui/views/tabs/tab_strip.cc

@@ -2276,7 +2276,8 @@ void TabStrip::SetDropIndex(int tab_data_index, bool drop_before) {
                                         &is_beneath);
 
   if (!drop_info_.get()) {
-    drop_info_.reset(new DropInfo(tab_data_index, drop_before, !is_beneath));
+    drop_info_.reset(
+        new DropInfo(tab_data_index, drop_before, !is_beneath, GetWidget()));
   } else {
     drop_info_->drop_index = tab_data_index;
     drop_info_->drop_before = drop_before;
@@ -2310,7 +2311,10 @@ gfx::ImageSkia* TabStrip::GetDropArrowImage(bool is_down) {
 
 // TabStrip::DropInfo ----------------------------------------------------------
 
-TabStrip::DropInfo::DropInfo(int drop_index, bool drop_before, bool point_down)
+TabStrip::DropInfo::DropInfo(int drop_index,
+                             bool drop_before,
+                             bool point_down,
+                             views::Widget* context)
     : drop_index(drop_index),
       drop_before(drop_before),
       point_down(point_down) {
@@ -2324,6 +2328,7 @@ TabStrip::DropInfo::DropInfo(int drop_index, bool drop_before, bool point_down)
   params.accept_events = false;
   params.can_activate = false;
   params.bounds = gfx::Rect(drop_indicator_width, drop_indicator_height);
+  params.context = context->GetNativeView();
   arrow_window->Init(params);
   arrow_window->SetContentsView(arrow_view);
 }

chrome/browser/ui/views/tabs/tab_strip.h

@@ -256,7 +256,10 @@ class TabStrip : public views::View,
   // Used during a drop session of a url. Tracks the position of the drop as
   // well as a window used to highlight where the drop occurs.
   struct DropInfo {
-    DropInfo(int index, bool drop_before, bool paint_down);
+    DropInfo(int drop_index,
+             bool drop_before,
+             bool point_down,
+             views::Widget* context);
     ~DropInfo();
 
     // Index of the tab to drop on. If drop_before is true, the drop should