Fix Telemetry to calculate bounding visible rect correctly.

tools/telemetry/telemetry/page/actions/scroll_unittest.py

Index: tools/telemetry/telemetry/page/actions/scroll_unittest.py
diff --git a/tools/telemetry/telemetry/page/actions/scroll_unittest.py b/tools/telemetry/telemetry/page/actions/scroll_unittest.py
index 98684f974a8e04264c4f361e10bc2597dd31eb2e..d4630381dc89ef1f26ea5aac832a0e3b49afdd59 100644
--- a/tools/telemetry/telemetry/page/actions/scroll_unittest.py
+++ b/tools/telemetry/telemetry/page/actions/scroll_unittest.py
@@ -80,7 +80,11 @@ class ScrollActionTest(tab_test_case.TabTestCase):
     # scrollable area being more than twice as tall as the viewport) would
     # result in a scroll location outside of the viewport bounds.
     self._tab.ExecuteJavaScript("""document.body.style.height =
-                           (2 * window.innerHeight + 1) + 'px';""")
+                           (3 * window.innerHeight + 1) + 'px';""")
+    self._tab.ExecuteJavaScript("""document.body.style.width =
+                           (3 * window.innerWidth + 1) + 'px';""")
+    self._tab.ExecuteJavaScript(
+        "window.scrollTo(window.innerWidth, window.innerHeight);")
 
     rect_top = int(self._tab.EvaluateJavaScript(
         '__GestureCommon_GetBoundingVisibleRect(document.body).top'))
@@ -97,6 +101,10 @@ class ScrollActionTest(tab_test_case.TabTestCase):
     viewport_height = int(self._tab.EvaluateJavaScript('window.innerHeight'))
     viewport_width = int(self._tab.EvaluateJavaScript('window.innerWidth'))
 
+    self.assertTrue(rect_top >= 0,
+        msg='%s >= %s' % (rect_top, 0))
+    self.assertTrue(rect_left >= 0,
+        msg='%s >= %s' % (rect_left, 0))
     self.assertTrue(rect_bottom <= viewport_height,
         msg='%s + %s <= %s' % (rect_top, rect_height, viewport_height))
     self.assertTrue(rect_right <= viewport_width,