Update pre-drag lifecycle for apps with shortcuts.

- First of all, deferred drag has been renamed to pre-drag
  to avoid confusion with the existing deferred end drag.
- For normal drags, the cycle is still startDrag -->
  onDragStart --> onDrop --> onDropComplete --> onDragEnd.
- Pre-drags have two additional callbacks: onPreDragStart
  and onPreDragEnd. onPreDragStart is called between
  startDrag and onDragStart, and onPreDragEnd is called
  at the same time as onDragStart or onDragEnd.
- If the pre-drag has not transitioned to a full drag before
  onDragEnd, onDragStart and onDropComplete are skipped
  (onDrop is still called to allow the DragView to animate).

Change-Id: Icd7a8f75d5fcc159f9a52758c22ab6eae3edb9e2
diff --git a/build.gradle b/build.gradle
index e103d79..0c00da9 100644
--- a/build.gradle
+++ b/build.gradle
@@ -3,7 +3,7 @@
         mavenCentral()
     }
     dependencies {
-        classpath 'com.android.tools.build:gradle:2.1.3'
+        classpath 'com.android.tools.build:gradle:2.2.0'
         classpath 'com.google.protobuf:protobuf-gradle-plugin:0.8.0'
     }
 }