Revert of Add getThemeColor to Tab and add plumbing for ChromeActivites.

Revert of Add getThemeColor to Tab and add plumbing for ChromeActivites. (patchset #3 id:40001 of https://codereview.chromium.org/1254423006/)

Reason for revert:
Speculative revert.
This seems to have broken
BrandColorTest.testBrandColorInterstitial
BrandColorTest.testNavigatingToBrandColorAndBack
BrandColorTest.testNoBrandColor
on Lollipop in Document Mde.

Original issue's description:
> Add getThemeColor to Tab and add plumbing for ChromeActivites.
>
> Moves all theme color computing logic to tab. Adds the necessary
> update signals to ChromeActivity and adds an onUpdate call to be
> overridden by extending classes.
>
> The main outcome of all this is, all ChromeActivities become color change aware. Doesn't add any visual changes. Yet.
>
> BUG=507340
>
> Committed: https://crrev.com/25d23c547cd7661fe2e679d74e4272917dae2985
> Cr-Commit-Position: refs/heads/master@{#341226}

TBR=dtrainor@chromium.org,yusufo@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG=507340
Committed: https://crrev.com/622bf10486216f89aaa3df8cd02a3daec638a53f
Cr-Commit-Position: refs/heads/master@{#341332}

[Fabrice (no longer in Chrome), 2015-07-31 15:13:34]

Created Revert of Add getThemeColor to Tab and add plumbing for ChromeActivites.

[commit-bot: I haz the power, 2015-07-31 15:14:32]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1260523004/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1260523004/1

[commit-bot: I haz the power, 2015-07-31 15:15:52]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2015-07-31 15:16:24]

Patchset 1 (id:??) landed as
https://crrev.com/622bf10486216f89aaa3df8cd02a3daec638a53f
Cr-Commit-Position: refs/heads/master@{#341332}