While screencasting a tab, do not disable rendering updates while hidden.

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

Index: chrome/browser/ui/views/tabs/tab_drag_controller.cc
diff --git a/chrome/browser/ui/views/tabs/tab_drag_controller.cc b/chrome/browser/ui/views/tabs/tab_drag_controller.cc
index c3980924258555be4adeb146fc11318f6f8da8a6..d0e2820b4b60a072219d30dc6f89f34b07a1b73d 100644
--- a/chrome/browser/ui/views/tabs/tab_drag_controller.cc
+++ b/chrome/browser/ui/views/tabs/tab_drag_controller.cc
@@ -1137,7 +1137,7 @@ void TabDragController::Attach(TabStrip* attached_tabstrip,
       }
 
       // Return the WebContents to normalcy.
-      source_dragged_contents()->SetCapturingContents(false);
+      source_dragged_contents()->DecrementCapturerCount();
     }
 
     // Inserting counts as a move. We don't want the tabs to jitter when the
@@ -1226,7 +1226,7 @@ void TabDragController::Detach(ReleaseCapture release_capture) {
   // Prevent the WebContents HWND from being hidden by any of the model
   // operations performed during the drag.
   if (!detach_into_browser_)
-    source_dragged_contents()->SetCapturingContents(true);
+    source_dragged_contents()->IncrementCapturerCount();
 
   std::vector<gfx::Rect> drag_bounds = CalculateBoundsForDraggedTabs(0);
   TabStripModel* attached_model = GetModel(attached_tabstrip_);
@@ -1660,6 +1660,13 @@ void TabDragController::RevertDrag() {
 
   if (detach_into_browser_ && source_tabstrip_)
     source_tabstrip_->GetWidget()->Activate();
+
+  // Return the WebContents to normalcy.  If the tab was attached to a
+  // TabStrip before the revert, the decrement has already occurred.
+  // If the tab was destroyed, don't attempt to dereference the
+  // WebContents pointer.
+  if (!detach_into_browser_ && !attached_tabstrip_ && source_dragged_contents())
+    source_dragged_contents()->DecrementCapturerCount();
 }
 
 void TabDragController::ResetSelection(TabStripModel* model) {
@@ -1805,6 +1812,10 @@ void TabDragController::CompleteDrag() {
             contentses, window_bounds, dock_info_, widget->IsMaximized());
     ResetSelection(new_browser->tab_strip_model());
     new_browser->window()->Show();
+
+    // Return the WebContents to normalcy.
+    if (!detach_into_browser_)
+      source_dragged_contents()->DecrementCapturerCount();
   }
 
   CleanUpHiddenFrame();