Cast ChromeShell into the fiery pit of Mount Doom.

This deletes the no-longer-used ChromeShell. Its raison d'être has been
supplanted by ChromePublic (the chrome_public_apk build target).
Goodbye, ChromeShell!

BUG=510220

Review URL: https://codereview.chromium.org/1314413004

Cr-Original-Commit-Position: refs/heads/master@{#347454}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: 44ce026f8450c71f6592beb02c7db825c1c4e82c

android/lint/suppressions.xml

@@ -54,9 +54,8 @@ Still reading?
     <ignore regexp=".*: data_reduction_illustration.png, reader_mode_bar_background.9.png, tabs_moved_htc.png, tabs_moved_nexus.png, tabs_moved_samsung.png$"/>
   </issue>
   <issue id="IconLocation">
-    <!-- It is OK for content_shell_apk and chrome_shell_apk to have missing assets. -->
+    <!-- It is OK for content_shell_apk to have missing assets. -->
     <ignore path="content/shell/android/java/res/"/>
-    <ignore path="chrome/android/shell/res/"/>
     <!-- Suppression for chrome/test/chromedriver/test/webview_shell/java/res/drawable/icon.png -->
     <ignore path="res/drawable/icon.png"/>
     <!-- TODO(lambroslambrou) remove this once crbug.com/502030 is fixed. -->