UIDevTools: Make exiting inspector mode work

Clicking ElementInspect button would toggle entering/exiting
inspector mode. However, previously clicking that button in
inspector mode would be handled by pinned element logic. In this
CL, we capture returned window element's active state. If the
window is not active, pinned element logic should not mark the
event as handled to give frontend a chance to handle the event.

BUG=899000

Change-Id: I4356f85f0ec6d90298473bb894f197aa4ab733e3
Reviewed-on: https://chromium-review.googlesource.com/c/1306403Reviewed-by: Leonard Grey <lgrey@chromium.org>
Commit-Queue: Wei Li <weili@chromium.org>
Cr-Commit-Position: refs/heads/master@{#604317}

components/ui_devtools/views/overlay_agent_aura.cc

@@ -19,6 +19,7 @@
 #include "ui/gfx/render_text.h"
 #include "ui/views/background.h"
 #include "ui/views/border.h"
+#include "ui/wm/core/window_util.h"
 
 namespace ui_devtools {
 
@@ -553,26 +554,35 @@ void OverlayAgentAura::OnMouseEvent(ui::MouseEvent* event) {
 
   // Find node id of element whose bounds contain the mouse pointer location.
   int element_id = FindElementIdTargetedByPoint(event);
+  if (!element_id)
+    return;
 
-  if (pinned_id_ == element_id) {
+#if defined(USE_AURA)
+  aura::Window* target = static_cast<aura::Window*>(event->target());
+  bool active_window = ::wm::IsActiveWindow(
+      target->GetRootWindow()->GetEventHandlerForPoint(event->root_location()));
+#else
+  bool active_window = true;
+#endif
+  if (pinned_id_ == element_id && active_window) {
     event->SetHandled();
     return;
   }
 
   // Pin the hover element on click.
   if (event->type() == ui::ET_MOUSE_PRESSED) {
+    if (active_window)
       event->SetHandled();
-    if (element_id)
     SetPinnedNodeId(element_id);
-  } else if (element_id && !pinned_id_) {
-    // Display only guidelines if hovering without a pinned element.
-    frontend()->nodeHighlightRequested(element_id);
-    HighlightNode(element_id, false /* show_size */);
-  } else if (element_id && pinned_id_) {
+  } else if (pinned_id_) {
     // If hovering with a pinned element, then show distances between the pinned
     // element and the hover element.
     HighlightNode(element_id, false /* show_size */);
     ShowDistancesInHighlightOverlay(pinned_id_, element_id);
+  } else {
+    // Display only guidelines if hovering without a pinned element.
+    frontend()->nodeHighlightRequested(element_id);
+    HighlightNode(element_id, false /* show_size */);
   }
 }