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

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

Index: remoting/android/java/src/org/chromium/chromoting/TrackingInputHandler.java
diff --git a/remoting/android/java/src/org/chromium/chromoting/TrackingInputHandler.java b/remoting/android/java/src/org/chromium/chromoting/TrackingInputHandler.java
index 2eaa14a267321f452b7f2340d1b48b1530995a48..13dd289631f4a36d2a49b88476a3da16a7d914e4 100644
--- a/remoting/android/java/src/org/chromium/chromoting/TrackingInputHandler.java
+++ b/remoting/android/java/src/org/chromium/chromoting/TrackingInputHandler.java
@@ -114,7 +114,10 @@ public class TrackingInputHandler implements TouchInputHandler {
             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) {
@@ -123,7 +126,9 @@ public class TrackingInputHandler implements TouchInputHandler {
             }
 
             // 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);