Ensure WebView is focused when handling an accessibility action.

When an Android accessibility service sends us a CLICK or FOCUS action
on a specific node in a WebView, we should first focus the WebView itself.
Otherwise clicking on a text field using an accessibility service doesn't
actually move input focus there and pop up the virtual keyboard.

Bug: 819669
Change-Id: I8e4069324e45516fbc1621723885ad8448fdc862
Reviewed-on: https://chromium-review.googlesource.com/953322Reviewed-by: Paul Miller <paulmiller@chromium.org>
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#541748}

content/public/android/java/src/org/chromium/content/browser/accessibility/WebContentsAccessibilityImpl.java

@@ -432,9 +432,11 @@ public class WebContentsAccessibilityImpl extends AccessibilityNodeProvider
                 }
                 return true;
             case AccessibilityNodeInfo.ACTION_CLICK:
+                if (!mView.hasFocus()) mView.requestFocus();
                 nativeClick(mNativeObj, virtualViewId);
                 return true;
             case AccessibilityNodeInfo.ACTION_FOCUS:
+                if (!mView.hasFocus()) mView.requestFocus();
                 nativeFocus(mNativeObj, virtualViewId);
                 return true;
             case AccessibilityNodeInfo.ACTION_CLEAR_FOCUS: