Bug 1330986 - Override proguard config to fix VectorDrawable corruption on Android 4 r=sebastian

See https://code.google.com/p/android/issues/detail?id=209558 . On Devices
running Android 4 and below, VectorDrawable's can be corrupted due
to overzealous proguarding. This doesn't appear to have been
fixed in the support library yet, and even if it were fixed we
still wouldn't be able to switch to the most modern support
library without significant work.

MozReview-Commit-ID: 3ByogGygCEd

--HG--
extra : rebase_source : 2adeed63f88ca39a71feec60627fb812b76d3bb4

mobile/android/config/proguard/appcompat-v7-keeps.cfg

@@ -9,3 +9,10 @@
 -keep public class * extends android.support.v4.view.ActionProvider {
     public <init>(android.content.Context);
 }
+
+-keepclassmembers class android.support.graphics.drawable.VectorDrawableCompat$* {
+   void set*(***);
+   *** get*();
+}
+
+-keepattributes LocalVariableTable