Remove ActionBar.LayoutParams MarginLayoutParams constructor

Adding this for L caused some fun issues with source compatibility.
Apps that previously passed another MarginLayoutParams subclass to
ActionBar.LayoutParams' constructor started statically linking to a
constructor overload that did not exist on older platform changes with
no other source changes. In the interests of avoiding these headaches
for developers, remove it.

Bug 15933193

Change-Id: I01cf8dfa2341b9d9629331639433b59352e7e15a

3 files changed, 30 insertions, 3 deletions

diff --git a/core/java/android/app/ActionBar.java b/core/java/android/app/ActionBar.java
index 628875f..5c98180 100644
--- a/core/java/android/app/ActionBar.java
+++ b/core/java/android/app/ActionBar.java
@@ -1334,8 +1334,14 @@ public abstract class ActionBar {
             super(source);
         }
 
-        public LayoutParams(MarginLayoutParams source) {
-            super(source);
-        }
+        /*
+         * Note for framework developers:
+         *
+         * You might notice that ActionBar.LayoutParams is missing a constructor overload
+         * for MarginLayoutParams. While it may seem like a good idea to add one, at this
+         * point it's dangerous for source compatibility. Upon building against a new
+         * version of the SDK an app can end up statically linking to the new MarginLayoutParams
+         * overload, causing a crash when running on older platform versions with no other changes.
+         */
     }
 }
diff --git a/core/java/android/view/ViewGroup.java b/core/java/android/view/ViewGroup.java
index 28e8bd6..36e5996 100644
--- a/core/java/android/view/ViewGroup.java
+++ b/core/java/android/view/ViewGroup.java
@@ -6476,6 +6476,20 @@ public abstract class ViewGroup extends View implements ViewParent, ViewManager
         }
 
         /**
+         * @hide Used internally.
+         */
+        public final void copyMarginsFrom(MarginLayoutParams source) {
+            this.leftMargin = source.leftMargin;
+            this.topMargin = source.topMargin;
+            this.rightMargin = source.rightMargin;
+            this.bottomMargin = source.bottomMargin;
+            this.startMargin = source.startMargin;
+            this.endMargin = source.endMargin;
+
+            this.mMarginFlags = source.mMarginFlags;
+        }
+
+        /**
          * Sets the margins, in pixels. A call to {@link android.view.View#requestLayout()} needs
          * to be done so that the new margins are taken into account. Left and right margins may be
          * overriden by {@link android.view.View#requestLayout()} depending on layout direction.
diff --git a/core/java/android/widget/Toolbar.java b/core/java/android/widget/Toolbar.java
index 122df2c..d140c82 100644
--- a/core/java/android/widget/Toolbar.java
+++ b/core/java/android/widget/Toolbar.java
@@ -1585,6 +1585,10 @@ public class Toolbar extends ViewGroup {
     /**
      * Layout information for child views of Toolbars.
      *
+     * <p>Toolbar.LayoutParams extends ActionBar.LayoutParams for compatibility with existing
+     * ActionBar API. See {@link android.app.Activity#setActionBar(Toolbar) Activity.setActionBar}
+     * for more info on how to use a Toolbar as your Activity's ActionBar.</p>
+     *
      * @attr ref android.R.styleable#Toolbar_LayoutParams_layout_gravity
      */
     public static class LayoutParams extends ActionBar.LayoutParams {
@@ -1624,6 +1628,9 @@ public class Toolbar extends ViewGroup {
 
         public LayoutParams(MarginLayoutParams source) {
             super(source);
+            // ActionBar.LayoutParams doesn't have a MarginLayoutParams constructor.
+            // Fake it here and copy over the relevant data.
+            copyMarginsFrom(source);
         }
 
         public LayoutParams(ViewGroup.LayoutParams source) {