app_list: Improve visual feedback for invalid touch scroll.

ui/app_list/apps_grid_view.cc

Index: ui/app_list/apps_grid_view.cc
diff --git a/ui/app_list/apps_grid_view.cc b/ui/app_list/apps_grid_view.cc
index 45b3c4a75c1107d9e87eb0c74f09d7c71176a6d6..a1b0a6c8a564d1d3795198b11a15e9f7b2e5f104 100644
--- a/ui/app_list/apps_grid_view.cc
+++ b/ui/app_list/apps_grid_view.cc
@@ -24,7 +24,11 @@ const int kPreferredTileWidth = 88;
 const int kPreferredTileHeight = 98;
 
 // Max extra column padding space in pixels for invalid page transition.
-const int kMaxExtraColPaddingForInvalidTransition = 80;
+const int kMaxExtraColPaddingForInvalidTransition = 15;
+
+// Extra column padding space in pixels of first column for invalid page
+// transition.
+const int kBaseExtraColPaddingForInvalidTransition = 50;
 
 }  // namespace
 
@@ -128,6 +132,8 @@ void AppsGridView::Layout() {
   const int transition_offset = is_valid ?
       transition.progress * page_width * dir :
       transition.progress * kMaxExtraColPaddingForInvalidTransition * dir;
+  const int base_transition_offset = is_valid ? 0 :
+      transition.progress * kBaseExtraColPaddingForInvalidTransition * dir;
 
   const int first_visible_index = current_page * tiles_per_page();
   const int last_visible_index = (current_page + 1) * tiles_per_page() - 1;
@@ -148,10 +154,11 @@ void AppsGridView::Layout() {
         x_offset += transition_offset;
     } else {
       const int col = i % cols_;
+      x_offset += base_transition_offset;
       if (transition_offset > 0)
-        x_offset += transition_offset * (col + 1);
+        x_offset += transition_offset * col;
       else
-        x_offset += transition_offset * (cols_ - col);
+        x_offset += transition_offset * (cols_ - col - 1);
     }
 
     gfx::Rect adjusted_slot(tile_slot);