Android: Make preview tab UI buttons easier to access

Increases the button padding so that it gets easier to recognize touch
events on the close/open-new-tab buttons on preview tab header.

Bug: 1050796
Change-Id: I9c74d98b36b7b50d1275afaa9d819d971a64d442
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2056192Reviewed-by: Matthew Jones <mdjones@chromium.org>
Commit-Queue: Jinsuk Kim <jinsukkim@chromium.org>
Cr-Commit-Position: refs/heads/master@{#744517}

chrome/android/java/res/layout/sheet_tab_toolbar.xml

@@ -50,23 +50,31 @@
 
             <org.chromium.ui.widget.ChromeImageView
                 android:id="@+id/close"
-                android:layout_width="24dp"
-                android:layout_height="24dp"
+                android:layout_width="40dp"
+                android:layout_height="40dp"
+                android:paddingTop="8dp"
+                android:paddingBottom="8dp"
+                android:paddingStart="8dp"
+                android:paddingEnd="8dp"
                 android:layout_alignParentEnd="true"
                 android:layout_alignParentBottom="true"
-                android:layout_marginBottom="14dp"
+                android:layout_marginBottom="6dp"
                 android:src="@drawable/btn_close"
                 android:contentDescription="@string/close"
                 app:tint="@color/default_icon_color" />
 
             <org.chromium.ui.widget.ChromeImageView
                 android:id="@+id/open_in_new_tab"
-                android:layout_width="24dp"
-                android:layout_height="24dp"
+                android:layout_width="40dp"
+                android:layout_height="40dp"
+                android:paddingTop="8dp"
+                android:paddingBottom="8dp"
+                android:paddingStart="8dp"
+                android:paddingEnd="8dp"
                 android:layout_toStartOf="@+id/close"
                 android:layout_alignParentBottom="true"
-                android:layout_marginEnd="24dp"
-                android:layout_marginBottom="14dp"
+                android:layout_marginEnd="8dp"
+                android:layout_marginBottom="6dp"
                 android:src="@drawable/open_in_new_tab"
                 android:contentDescription="@string/contextmenu_open_in_new_tab"
                 android:visibility="gone"