[Android Chromoting] Center the desktop if it is smaller than the screen.

remoting/android/java/src/org/chromium/chromoting/TrackingInputHandler.java

 // Copyright 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 package org.chromium.chromoting;
 
 import android.content.Context;
 import android.graphics.Matrix;
 import android.graphics.PointF;
 import android.util.Log;
@@ skipping 96 matching lines @@
             float[] rectScreen = {0, 0, mRenderData.imageWidth, mRenderData.imageHeight};
             mRenderData.transform.mapPoints(rectScreen);
 
             float leftDelta = rectScreen[0];
             float rightDelta = rectScreen[2] - mRenderData.screenWidth;
             float topDelta = rectScreen[1];
             float bottomDelta = rectScreen[3] - mRenderData.screenHeight;
             float xAdjust = 0;
             float yAdjust = 0;
 
-            if (leftDelta > 0 && rightDelta > 0) {
+            if (rectScreen[2] - rectScreen[0] < mRenderData.screenWidth) {
+                // Image is narrower than the screen, so center it.
+                xAdjust = -(rightDelta + leftDelta) / 2;
+            } else if (leftDelta > 0 && rightDelta > 0) {
                 // Panning the image left will show more of it.
                 xAdjust = -Math.min(leftDelta, rightDelta);
             } else if (leftDelta < 0 && rightDelta < 0) {
                 // Pan the image right.
                 xAdjust = Math.min(-leftDelta, -rightDelta);
             }
 
             // Apply similar logic for yAdjust.
-            if (topDelta > 0 && bottomDelta > 0) {
+            if (rectScreen[3] - rectScreen[1] < mRenderData.screenHeight) {
+                yAdjust = -(bottomDelta + topDelta) / 2;
+            } else if (topDelta > 0 && bottomDelta > 0) {
                 yAdjust = -Math.min(topDelta, bottomDelta);
             } else if (topDelta < 0 && bottomDelta < 0) {
                 yAdjust = Math.min(-topDelta, -bottomDelta);
             }
 
             mRenderData.transform.postTranslate(xAdjust, yAdjust);
         }
         mViewer.transformationChanged();
     }
 
@@ skipping 127 matching lines @@
             return true;
         }
 
         /** Called when the user is done zooming. Defers to onScale()'s judgement. */
         @Override
         public void onScaleEnd(ScaleGestureDetector detector) {
             onScale(detector);
         }
     }
 }