[AW] DevUI: Fix shared alert icon color

Drawables all share the same state across the app. Changing the icon
color in the bottom nav bar when switching fragments changes in all
Drawables using the same resource. Calling Drawable#mutate() makes
this Drawable mutable so that it doesn't share its state anymore.

Fixed: 1069679
Test: Switch fragments and observe error view icon color
Change-Id: I7c2d3c1ace7b3119de91e959ee4c5b9b3321a2dc
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2161228
Auto-Submit: Hazem Ashmawy <hazems@chromium.org>
Commit-Queue: Nate Fischer <ntfschr@chromium.org>
Reviewed-by: Nate Fischer <ntfschr@chromium.org>
Cr-Commit-Position: refs/heads/master@{#762101}

android_webview/nonembedded/java/src/org/chromium/android_webview/devui/MainActivity.java

@@ -112,6 +112,7 @@ public class MainActivity extends FragmentActivity {
                                            : getResources().getColor(R.color.navigation_unselected);
             for (Drawable drawable : textView.getCompoundDrawables()) {
                 if (drawable != null) {
+                    drawable.mutate();
                     drawable.setColorFilter(
                             new PorterDuffColorFilter(color, PorterDuff.Mode.SRC_IN));
                 }