Bug 705505 - Extend panzoom threshold. r=kats

mobile/android/base/ui/PanZoomController.java

@@ -83,8 +83,8 @@ public class PanZoomController
     // values make the animation more accurate, but slower to plot.
     private static final int SUBDIVISION_COUNT = 1000;
     // The distance the user has to pan before we recognize it as such (e.g. to avoid
-    // 1-pixel pans between the touch-down and touch-up of a click)
-    private static final float PAN_THRESHOLD = 4.0f;
+    // 1-pixel pans between the touch-down and touch-up of a click). In units of inches.
+    private static final float PAN_THRESHOLD = 0.1f;
     // Angle from axis within which we stay axis-locked
     private static final double AXIS_LOCK_ANGLE = Math.PI / 6.0; // 30 degrees
     // The maximum velocity change factor between events, per ms, in %.
@@ -179,7 +179,7 @@ public class PanZoomController
             Log.e(LOGTAG, "Received impossible touch move while in " + mState);
             return false;
         case TOUCHING:
-            if (panDistance(event) < PAN_THRESHOLD)
+            if (panDistance(event) < PAN_THRESHOLD * GeckoAppShell.getDpi())
                 return false;
             // fall through
         case PANNING_HOLD_LOCKED: