Re-enable TouchSelectionOriginatingFromWebpageTest with some fixes and logs

ui/views/touchui/touch_selection_controller_impl.cc

 // Copyright (c) 2013 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 "ui/views/touchui/touch_selection_controller_impl.h"
 
 #include "base/time/time.h"
 #include "grit/ui_resources.h"
 #include "grit/ui_strings.h"
 #include "ui/base/resource/resource_bundle.h"
@@ skipping 175 matching lines @@
     canvas->DrawImageInt(*GetHandleImage()->ToImageSkia(),
         kSelectionHandleHorizPadding, cursor_height());
   }
 
   virtual void OnGestureEvent(ui::GestureEvent* event) OVERRIDE {
     event->SetHandled();
     switch (event->type()) {
       case ui::ET_GESTURE_SCROLL_BEGIN:
         widget_->SetCapture(this);
         controller_->SetDraggingHandle(this);
-        drag_offset_ = event->y() - cursor_height() -
+        drag_offset_ = event->y() - cursor_height() +
             kSelectionHandleVerticalDragOffset;
         break;
       case ui::ET_GESTURE_SCROLL_UPDATE: {
         gfx::Point drag_pos(event->location().x(),
             event->location().y() - drag_offset_);
         controller_->SelectionHandleDragged(drag_pos);
         break;
       }
       case ui::ET_GESTURE_SCROLL_END:
       case ui::ET_SCROLL_FLING_START:
@@ skipping 45 matching lines @@
     if (draw_invisible_ == draw_invisible)
       return;
     draw_invisible_ = draw_invisible;
     SchedulePaint();
   }
 
  private:
   scoped_ptr<Widget> widget_;
   TouchSelectionControllerImpl* controller_;
   gfx::Rect selection_rect_;
+
+  // Vertical offset between the scroll event position and the drag position
+  // reported to the client view (see the ASCII figure at the top of the file
+  // and its description for more details).
   int drag_offset_;
 
   // If set to true, the handle will not draw anything, hence providing an empty
   // widget. We need this because we may want to stop showing the handle while
   // it is being dragged. Since it is being dragged, we cannot destroy the
   // handle.
   bool draw_invisible_;
 
   DISALLOW_COPY_AND_ASSIGN(EditingHandleView);
 };
@@ skipping 258 matching lines @@
 }
 
 ui::TouchSelectionController* ViewsTouchSelectionControllerFactory::create(
     ui::TouchEditable* client_view) {
   if (switches::IsTouchEditingEnabled())
     return new views::TouchSelectionControllerImpl(client_view);
   return NULL;
 }
 
 }  // namespace views