Revert "Enable chrome.automation.getDesktop on all aura platforms."

Revert "Enable chrome.automation.getDesktop on all aura platforms."

This reverts commit 35b188a996e59c65787207818c7b90d70007f03d.

Caused browser_tests AutomationApiTest.DesktopLoadTabs to fail

e.g.:
https://build.chromium.org/p/chromium.linux/builders/Linux%20Tests/builds/22541

"""
AutomationApiTest.DesktopLoadTabs (run #1):
[ RUN      ] AutomationApiTest.DesktopLoadTabs
Xlib:  extension "RANDR" missing on display ":9".
Xlib:  extension "RANDR" missing on display ":9".
[25828:25828:0327/163831:INFO:audio_manager_pulse.cc(258)] Failed to connect to the context.  Error: Connection refused
[25828:25932:0327/163832:WARNING:data_reduction_proxy_config.cc(330)] SPDY proxy OFF at startup
[25828:25828:0327/163832:WARNING:password_store_factory.cc(259)] Using basic (unencrypted) store for password storage. See http://code.google.com/p/chromium/wiki/LinuxPasswordStorage for more information about password storage options.
[25828:25828:0327/163832:INFO:CONSOLE(0)] "calling getTree() callback", source: chrome-extension://mojndmjfhfgjjicpoiodenhflfmkopil/load_tabs.html (0)
[25828:25828:0327/163832:INFO:CONSOLE(0)] "calling getTree() callback", source: chrome-extension://mojndmjfhfgjjicpoiodenhflfmkopil/load_tabs.html (0)
[25828:25828:0327/163832:INFO:CONSOLE(0)] "[FAIL] testLoadTabs: uncaught exception: Cannot read property 'firstChild' of undefined: TypeError: Cannot read property 'firstChild' of undefined
    at testLoadTabs (chrome-extension://mojndmjfhfgjjicpoiodenhflfmkopil/load_tabs.js:28:36)
"""

NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=Original Patch Had No Bug!?!
TBR=dmazzoni@chromium.org, oshima@chromium.org, sky@chromium.org, dtseng@chromium.org

Committed: https://chromium.googlesource.com/chromium/src/+/49fdb401fce873c6390f2df5bce2deac2921ee93

[commit-bot: I haz the power, 2015-03-28 00:21:20]

Patchset 1 (id:??) landed as
https://crrev.com/49fdb401fce873c6390f2df5bce2deac2921ee93
Cr-Commit-Position: refs/heads/master@{#322684}

[scheib, 2015-03-28 00:21:32]

Committed patchset #1 (id:1) manually as
49fdb401fce873c6390f2df5bce2deac2921ee93 (presubmit successful).