Implement sendKeyEvent print preview function for OOP PDF.

Implement sendKeyEvent print preview function for OOP PDF.

This implements the function which sends certain key events to the PDF plugin.
This allows the document to be scrolled even when it isn't focused.

BUG=303491
Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=273823

[Lei Zhang, 2014-05-28 22:23:54]

lgtm with a question:

https://codereview.chromium.org/282113004/diff/1/chrome/browser/resources/pdf...
File chrome/browser/resources/pdf/viewport.js (right):

https://codereview.chromium.org/282113004/diff/1/chrome/browser/resources/pdf...
chrome/browser/resources/pdf/viewport.js:57: * The increment to scroll a page by
in pixels when up/down/left/right arrow
Does this matter if we are on a hidpi screen?

[raymes, 2014-05-30 07:10:37]

https://codereview.chromium.org/282113004/diff/1/chrome/browser/resources/pdf...
File chrome/browser/resources/pdf/viewport.js (right):

https://codereview.chromium.org/282113004/diff/1/chrome/browser/resources/pdf...
chrome/browser/resources/pdf/viewport.js:57: * The increment to scroll a page by
in pixels when up/down/left/right arrow
No it shouldn't. All the measurements are in device independent pixels

[raymes, 2014-05-30 07:41:54]

The CQ bit was checked by raymes@chromium.org

[commit-bot: I haz the power, 2014-05-30 07:43:17]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/raymes@chromium.org/282113004/20001

[raymes, 2014-05-30 07:44:19]

The CQ bit was checked by raymes@chromium.org

[commit-bot: I haz the power, 2014-05-30 07:46:08]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/raymes@chromium.org/282113004/40001

[commit-bot: I haz the power, 2014-05-30 12:20:41]

FYI, CQ is re-trying this CL (attempt #1).
The failing builders are:
  android_dbg_triggered_tests on tryserver.chromium
(http://build.chromium.org/p/tryserver.chromium/builders/android_dbg_triggered...)

[commit-bot: I haz the power, 2014-05-30 13:33:39]

Change committed as 273823