Android: Gesture Navigation peeks 1.5 items

Peek 1.5 items to give first-time gesture users a sense
of what's in the list.

Bug: 1015004
Change-Id: I908426d659cceedee590b83ce573d360e257ddc8
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1865920Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707144}

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

@@ -680,7 +680,7 @@
     <dimen name="navigation_sheet_content_top_padding">18dp</dimen>
     <dimen name="navigation_sheet_content_bottom_padding">4dp</dimen>
     <dimen name="navigation_sheet_content_wrap_padding">12dp</dimen>
-    <dimen name="navigation_sheet_peek_height">64dp</dimen>
+    <dimen name="navigation_sheet_peek_height">120dp</dimen>
 
     <!-- ChromeTextInputLayout dimensions -->
     <dimen name="text_input_layout_padding_start">3dp</dimen>