Fix crash when dragging Select to Speak box and mousewheel event.

Bug: 1047957
Change-Id: Ied78b3132b920698f7e5178c72e1583627f10b49
AX-Relnotes: Fixes crash when dragging STS box and doing a mousewheel.
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2216376Reviewed-by: Anastasia Helfinstein <anastasi@google.com>
Commit-Queue: Katie Dektar <katie@chromium.org>
Cr-Commit-Position: refs/heads/master@{#772067}

chrome/browser/chromeos/accessibility/select_to_speak_browsertest.cc

@@ -306,6 +306,27 @@ IN_PROC_BROWSER_TEST_F(SelectToSpeakTestWithLanguageDetection,
   sm_.Replay();
 }
 
+IN_PROC_BROWSER_TEST_F(SelectToSpeakTest, DoesNotCrashWithMousewheelEvent) {
+  ui_test_utils::NavigateToURL(
+      browser(), GURL("data:text/html;charset=utf-8,<p>This is some text</p>"));
+  gfx::Rect bounds = GetWebContentsBounds();
+
+  // Hold down Search and drag over the web contents to select everything.
+  generator_->PressKey(ui::VKEY_LWIN, 0 /* flags */);
+  generator_->MoveMouseTo(bounds.x(), bounds.y());
+  generator_->PressLeftButton();
+  // Ensure this does not crash. It should have no effect.
+  generator_->MoveMouseWheel(10, 10);
+  generator_->MoveMouseTo(bounds.x() + bounds.width(),
+                          bounds.y() + bounds.height());
+  generator_->MoveMouseWheel(100, 5);
+  generator_->ReleaseLeftButton();
+  generator_->ReleaseKey(ui::VKEY_LWIN, 0 /* flags */);
+
+  sm_.ExpectSpeechPattern("This is some text*");
+  sm_.Replay();
+}
+
 // Flaky test: crbug.com/950049.
 IN_PROC_BROWSER_TEST_F(SelectToSpeakTest, DISABLED_FocusRingMovesWithMouse) {
   // Create a callback for the focus ring observer.

chrome/browser/chromeos/accessibility/select_to_speak_event_handler_delegate.cc

@@ -54,6 +54,10 @@ void SelectToSpeakEventHandlerDelegate::DispatchMouseEvent(
   // don't ever try to run this code on some other thread.
   DCHECK(content::BrowserThread::CurrentlyOn(content::BrowserThread::UI));
 
+  // MouseWheel not handled by ui::MakeWebMouseEvent.
+  if (event.type() == ui::EventType::ET_MOUSEWHEEL)
+    return;
+
   extensions::ExtensionHost* host = chromeos::GetAccessibilityExtensionHost(
       extension_misc::kSelectToSpeakExtensionId);
   if (!host)