Default to visible in GifDrawable.

Fixes #130.

library/src/androidTest/java/com/bumptech/glide/load/resource/gif/GifDrawableTest.java

@@ -68,6 +68,21 @@ public class GifDrawableTest {
         verify(frameManager).getNextFrame(eq(drawable));
     }
 
+    @Test
+    public void testRequestsNextFrameOnStartWithoutCallToSetVisible() {
+        drawable.start();
+
+        verify(frameManager).getNextFrame(eq(drawable));
+    }
+
+    @Test
+    public void testDoesNotRequestNextFrameOnStartIfGotCallToSetVisibleWithVisibleFalse() {
+        drawable.setVisible(false, false);
+        drawable.start();
+
+        verify(frameManager, never()).getNextFrame(eq(drawable));
+    }
+
     @Test
     public void testShouldInvalidateSelfOnRun() {
         drawable.setVisible(true, true);

library/src/main/java/com/bumptech/glide/load/resource/gif/GifDrawable.java

@@ -33,8 +33,12 @@ public class GifDrawable extends GlideDrawable implements GifFrameManager.FrameC
     private boolean isStarted;
     /** True if the drawable's resources have been recycled. */
     private boolean isRecycled;
-    /** True if the drawable is currently visible. */
-    private boolean isVisible;
+    /**
+     * True if the drawable is currently visible. Default to true because on certain platforms (at least 4.1.1),
+     * setVisible is not called on {@link android.graphics.drawable.Drawable Drawables} during
+     * {@link android.widget.ImageView#setImageDrawable(android.graphics.drawable.Drawable)}. See issue #130.
+     */
+    private boolean isVisible = true;
     /** The number of times we've looped over all the frames in the gif. */
     private int loopCount;
     /** The number of times to loop through the gif animation. */