Add in dummy mipmap/splash_icon_xx[x]hdpi resources

This is to sync the client/server R.txt files

Change-Id: Iaed949845032ec14c951b3d5d45c62839f282826
Reviewed-on: https://chromium-review.googlesource.com/c/1246953
Commit-Queue: Glenn Hartmann <hartmanng@chromium.org>
Reviewed-by: Peter Kotwicz <pkotwicz@chromium.org>
Cr-Commit-Position: refs/heads/master@{#595906}

chrome/android/webapk/shell_apk/current_version/current_version.gni

@@ -12,4 +12,4 @@
 # //chrome/android/webapk/shell_apk:webapk is changed. This includes
 # Java files, Android resource files and AndroidManifest.xml. Does not affect
 # Chrome.apk
-current_shell_apk_version = 58
+current_shell_apk_version = 59

chrome/android/webapk/shell_apk/res/drawable-xxhdpi/splash_icon.xml

@@ -4,4 +4,4 @@
      found in the LICENSE file. -->
 
 <bitmap xmlns:android="http://schemas.android.com/apk/res/android"
-    android:src="@mipmap/app_icon_xxxhdpi"/>
+    android:src="@mipmap/splash_icon_xxhdpi"/>

chrome/android/webapk/shell_apk/res/drawable-xxxhdpi/splash_icon.xml

@@ -4,4 +4,4 @@
      found in the LICENSE file. -->
 
 <bitmap xmlns:android="http://schemas.android.com/apk/res/android"
-    android:src="@mipmap/app_icon_xxxhdpi"/>
+    android:src="@mipmap/splash_icon_xxxhdpi"/>