Revert of Change app icon to @mipmap/ic_launcher (patchset chromium#2 …

…id:20001 of https://codereview.chromium.org/2793213002/ )

Reason for revert:
This broke the icon on numerous devices. Reverting for now, will investigate and reland.

Original issue's description:
> Change app icon to @mipmap/ic_launcher
>
> The v17 version of ic_launcer points to the old app_icon.png. The v26 version will support adaptive icons.
>
> BUG=707449
>
> Review-Url: https://codereview.chromium.org/2793213002
> Cr-Commit-Position: refs/heads/master@{#462139}
> Committed: https://chromium.googlesource.com/chromium/src/+/e620ab8ad484d94fa90daf44802f9e99c2aaa65f

TBR=tedchoc@chromium.org
# Skipping CQ checks because original CL landed less than 1 days ago.
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=707449

Review-Url: https://codereview.chromium.org/2801713005
Cr-Commit-Position: refs/heads/master@{#462473}

chrome/android/java/AndroidManifest.xml

@@ -110,7 +110,7 @@ by a child template that "extends" this file.
     <!-- Set android:largeHeap to "true" to allow more than the default
          Java heap limit (32Mb on Nexus S, 48Mb on Xoom). -->
     <application android:name="{% block application_name %}org.chromium.chrome.browser.ChromeApplication{% endblock %}"
-        android:icon="@mipmap/ic_launcher"
+        android:icon="@mipmap/app_icon"
         android:label="@string/app_name"
         android:largeHeap="false"
         android:manageSpaceActivity="@string/manage_space_activity"