[TTS] Fix bottom padding for IPH bubble

This CL decreases the bottom padding of the In-Product Help bubbles for
Contextual Search, to overlap the panel, as per UI Review's comment.

Bug: 794013
Change-Id: I607f5ea31f3cea0cbd370b9a3b19fddd6b8db385
Reviewed-on: https://chromium-review.googlesource.com/829879
Commit-Queue: Theresa <twellington@chromium.org>
Reviewed-by: Theresa <twellington@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524437}

chrome/android/java/res/values/dimens.xml

@@ -118,7 +118,7 @@
     <dimen name="contextual_search_end_button_width">48dp</dimen>
     <dimen name="contextual_search_divider_line_width">1dp</dimen>
     <dimen name="contextual_search_divider_line_height">24dp</dimen>
-    <dimen name="contextual_search_bubble_y_inset">14dp</dimen>
+    <dimen name="contextual_search_bubble_y_inset">-3dp</dimen>
 
     <!-- Overlay panel dimensions -->
     <dimen name="overlay_panel_bar_height">56dp</dimen>