Implement resolving of icon attributes to resIds in AlertController

Platform code using AlertController directly currently has
no way to set the correct theme-specific dialog icon in a
generic way. This adds code to handle such usage.

Change-Id: I48beafa1183e4edf6d5378b3985a7f9be5fcda8b

Author: blunden

core/java/com/android/internal/app/AlertController.java

@@ -347,6 +347,18 @@ public void setIcon(Drawable icon) {
         }
     }
 
+    /**
+     * @param attrId the attributeId of the theme-specific drawable
+     * to resolve the resourceId for.
+     *
+     * @return resId the resourceId of the theme-specific drawable
+     */
+    public int getIconAttributeResId(int attrId) {
+        TypedValue out = new TypedValue();
+        mContext.getTheme().resolveAttribute(attrId, out, true);
+        return out.resourceId;
+    }
+
     public void setInverseBackgroundForced(boolean forceInverseBackground) {
         mForceInverseBackground = forceInverseBackground;
     }
@@ -740,6 +752,7 @@ public static class AlertParams {
 
         public int mIconId = 0;
         public Drawable mIcon;
+        public int mIconAttrId = 0;
         public CharSequence mTitle;
         public View mCustomTitleView;
         public CharSequence mMessage;
@@ -806,6 +819,9 @@ public void apply(AlertController dialog) {
                 if (mIconId >= 0) {
                     dialog.setIcon(mIconId);
                 }
+                if (mIconAttrId > 0) {
+                    dialog.setIcon(dialog.getIconAttributeResId(mIconAttrId));
+                }
             }
             if (mMessage != null) {
                 dialog.setMessage(mMessage);