[TTS] Fix bug with IPH bubble position in Multiwindow mode

This CL fixes an issue that caused the In-Prodcut Help UI for Contextual
Search to appear at the bottom of the screen, over the Contextual Search
panel in multiwindow mode.

Bug: 794732
Change-Id: Ie9e83fe51621cd477502c851899dca7d68c333b0
Reviewed-on: https://chromium-review.googlesource.com/830809Reviewed-by: Donn Denman <donnd@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Commit-Queue: Donn Denman <donnd@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524487}

chrome/android/java/src/org/chromium/chrome/browser/compositor/bottombar/contextualsearch/ContextualSearchPanel.java

@@ -611,14 +611,15 @@ public class ContextualSearchPanel extends OverlayPanel {
      *         the screen, in pixels.
      */
     public Rect getPanelRect() {
-        Rect visibleDisplayFrame = new Rect();
-        mActivity.getWindow().getDecorView().getWindowVisibleDisplayFrame(visibleDisplayFrame);
+        int[] contentLocationInWindow = new int[2];
+        mActivity.findViewById(android.R.id.content).getLocationInWindow(contentLocationInWindow);
+        int leftPadding = contentLocationInWindow[0];
+        int topPadding = contentLocationInWindow[1];
 
         // getOffsetX() and getOffsetY() return the position of the panel relative to the activity,
-        // therefore visibleDisplayFrame.left and visibleDisplayFrame.top are added to get the
-        // position in the screen.
-        int left = (int) (getOffsetX() / mPxToDp) + visibleDisplayFrame.left;
-        int top = (int) ((getOffsetY()) / mPxToDp) + visibleDisplayFrame.top;
+        // therefore leftPadding and topPadding are added to get the position in the screen.
+        int left = (int) (getOffsetX() / mPxToDp) + leftPadding;
+        int top = (int) (getOffsetY() / mPxToDp) + topPadding;
         int bottom = top + (int) (getBarHeight() / mPxToDp);
         int right = left + (int) (getWidth() / mPxToDp);