Add ScrollPageToElement to action_runner.

telemetry/telemetry/internal/testing/page_with_swipeables.html

Index: telemetry/telemetry/internal/testing/page_with_swipeables.html
diff --git a/telemetry/telemetry/internal/testing/page_with_swipeables.html b/telemetry/telemetry/internal/testing/page_with_swipeables.html
index bd209dcfb2f26969c2f85f8da6ab0cf9217ad11a..8844bb912fdd8d38d6344a27e6d1a9d7f4dd1679 100644
--- a/telemetry/telemetry/internal/testing/page_with_swipeables.html
+++ b/telemetry/telemetry/internal/testing/page_with_swipeables.html
@@ -48,5 +48,6 @@
 
 <div class="tall-and-wide"></div>
 
+<div id="off-screen"></div>

[nednguyen, 2016/10/13 23:13:48]

How can we be sure that this is off screen?

[rnephew (Reviews Here), 2016/10/14 00:13:18]

The div above it is 5000x5000 pixels in size, so thats not a guarantee it'll be
off screen I guess, but its a good indicator that it should be at first.

[nednguyen, 2016/10/14 00:19:02]

Ah I see. In your test, can you first assert that it's off screen?

 </body>

[nednguyen, 2016/10/14 00:19:02]

can you s.t like another tall-and-wide, then another off screen element? Would
be nice to check scrolling  down to get into the element, then scroll up to get
to another element.

[charliea (OOO until 10-5), 2016/10/14 03:34:29]

+1

Without this, we can't really have any confidence that scrolling up works.

 </html>