[Media Controls] Reland Prevent ComputedStyleRef crash

This CL re-adds the null checks for internal_button_ and
GetComputedStyle on the overlay play button. These were added to
prevent a crash, then removed when the crash was not fixed and replaced
with a different null check. However, it looks like we actually need
these too, so we're adding them back.

Bug: 870490
Change-Id: I1c6ad4b3f1dc36c7a2149a06c4f42f8ca00fb589
Reviewed-on: https://chromium-review.googlesource.com/1187710Reviewed-by: Becca Hughes <beccahughes@chromium.org>
Commit-Queue: Tommy Steimel <steimel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#585719}

third_party/blink/renderer/modules/media_controls/elements/media_control_overlay_play_button_element.cc

@@ -296,13 +296,12 @@ bool MediaControlOverlayPlayButtonElement::ShouldCausePlayPause(
 
 bool MediaControlOverlayPlayButtonElement::IsMouseEventOnInternalButton(
     const MouseEvent& mouse_event) const {
-  // If no position data available, default to yes.
-  if (!mouse_event.HasPosition())
-    return true;
-
-  // If there is no layout view, default to yes.
-  if (!GetDocument().GetLayoutView())
+  // If we don't have the necessary pieces to calculate whether the event is
+  // within the bounds of the button, default to yes.
+  if (!mouse_event.HasPosition() || !internal_button_ ||
+      !GetDocument().GetLayoutView() || !GetComputedStyle()) {
     return true;
+  }
 
   // Find the zoom-adjusted internal button bounding box.
   DOMRect* box = internal_button_->getBoundingClientRect();

third_party/blink/renderer/modules/media_controls/elements/media_control_overlay_play_button_element_test.cc

@@ -7,6 +7,7 @@
 #include "testing/gtest/include/gtest/gtest.h"
 #include "third_party/blink/renderer/core/css/css_property_value_set.h"
 #include "third_party/blink/renderer/core/dom/events/event.h"
+#include "third_party/blink/renderer/core/dom/node_computed_style.h"
 #include "third_party/blink/renderer/core/event_type_names.h"
 #include "third_party/blink/renderer/core/events/mouse_event.h"
 #include "third_party/blink/renderer/core/html/html_html_element.h"
@@ -17,11 +18,28 @@
 
 namespace blink {
 
-class MediaControlOverlayPlayButtonElementTest : public PageTestBase {
+class MediaControlOverlayPlayButtonElementTest
+    : public PageTestBase,
+      private ScopedModernMediaControlsForTest {
  public:
+  MediaControlOverlayPlayButtonElementTest()
+      : ScopedModernMediaControlsForTest(true) {}
+
   void SetUp() final {
-    // Create page and instance of AnimatedArrow to run tests on.
+    // Create page with video element with controls.
     PageTestBase::SetUp();
+    HTMLVideoElement* media_element = HTMLVideoElement::Create(GetDocument());
+    media_element->SetBooleanAttribute(HTMLNames::controlsAttr, true);
+    GetDocument().body()->AppendChild(media_element);
+
+    // Create instance of MediaControlOverlayPlayButtonElement for tests.
+    MediaControlsImpl* media_controls =
+        static_cast<MediaControlsImpl*>(media_element->GetMediaControls());
+    ASSERT_NE(nullptr, media_controls);
+    overlay_play_button_ =
+        new MediaControlOverlayPlayButtonElement(*media_controls);
+
+    // Create instance of AnimatedArrow to run tests on.
     arrow_element_ = new MediaControlOverlayPlayButtonElement::AnimatedArrow(
         "test", GetDocument());
     GetDocument().body()->AppendChild(arrow_element_);
@@ -47,6 +65,16 @@ class MediaControlOverlayPlayButtonElementTest : public PageTestBase {
     GetElementById("arrow-3")->DispatchEvent(*event);
   }
 
+  void RemoveInternalButton() {
+    overlay_play_button_->internal_button_ = nullptr;
+  }
+
+  void EnsureNoComputedStyle() {
+    // Due to the nature of the test setup, we already get a null computedstyle
+    // for free :). Just make sure it's actually not there.
+    ASSERT_EQ(nullptr, overlay_play_button_->GetComputedStyle());
+  }
+
   Document& CreateTestDocumentWithBody() {
     Document* document = Document::CreateForTest();
     HTMLHtmlElement* html = HTMLHtmlElement::Create(*document);
@@ -118,9 +146,20 @@ TEST_F(MediaControlOverlayPlayButtonElementTest, ShowIncrementsCounter) {
   ExpectPresentAndShown();
 }
 
+TEST_F(MediaControlOverlayPlayButtonElementTest,
+       KeepEventInNodeWithoutInternalButtonDoesntCrash) {
+  RemoveInternalButton();
+  SimulateKeepEventInNode();
+}
+
+TEST_F(MediaControlOverlayPlayButtonElementTest,
+       KeepEventInNodeWithoutComputedStyleDoesntCrash) {
+  EnsureNoComputedStyle();
+  SimulateKeepEventInNode();
+}
+
 TEST_F(MediaControlOverlayPlayButtonElementTest,
        KeepEventInNodeWithoutLayoutViewDoesntCrash) {
-  ScopedModernMediaControlsForTest enable_modern_media_controls(true);
   Document& document_without_layout_view = CreateTestDocumentWithBody();
   CreateTestOverlayPlayButton(document_without_layout_view);
   SimulateKeepEventInNode();