Revert of html_viewer: Add DevToolsAgentImpl.

Revert of html_viewer: Add DevToolsAgentImpl. (patchset #5 id:80001 of https://codereview.chromium.org/1163953002/)

Reason for revert:
Maybe the reason of the html_viewer_apptests flakiness:

http://build.chromium.org/p/chromium.mojo/builders/Chromium%20Mojo%20Linux/builds/9552

Running mojo:html_viewer_apptests...
DEBUG:Tests for mojo:html_viewer_apptests:
AXProviderTest.
  HelloWorld

DEBUG:Command: /mnt/data/b/build/slave/chromium_mojo/build/src/out/Release/mojo_runner --gtest_filter=AXProviderTest.HelloWorld mojo:html_viewer_apptests

[  FAILED  ] Command (exit code -11): /mnt/data/b/build/slave/chromium_mojo/build/src/out/Release/mojo_runner --gtest_filter=AXProviderTest.HelloWorld mojo:html_viewer_apptests

Original issue's description:
> html_viewer: Add DevToolsAgentImpl.
>
> DevToolsAgentImpl connects the DevTools mojo service with the DevTools agent support in blink.
>
> BUG=478249
>
> Committed: https://crrev.com/32166090d27c6450957f59eedaa6ea5fa12762e4
> Cr-Commit-Position: refs/heads/master@{#333516}

TBR=sky@chromium.org,dgozman@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=478249
Committed: https://crrev.com/2008a972161fbf2359fe77c67d16f36539f8098b
Cr-Commit-Position: refs/heads/master@{#333570}

[yzshen1, 2015-06-09 20:55:15]

Created Revert of html_viewer: Add DevToolsAgentImpl.

[commit-bot: I haz the power, 2015-06-09 20:57:51]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1172123002/1

[commit-bot: I haz the power, 2015-06-09 21:00:06]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-06-09 21:00:54]

Patchset 1 (id:??) landed as
https://crrev.com/2008a972161fbf2359fe77c67d16f36539f8098b
Cr-Commit-Position: refs/heads/master@{#333570}