On enterprise machines read policy from the registry.

This will allow the usage of third party policy management
software in enteprise deployments of Chrome on Windows.

BUG=259236

Review URL: https://codereview.chromium.org/152633003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253358 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253358
Store signature key and encryption key in case syncing hasn't started.

When a supervised user is created, it can happen that the syncing
hasn't started already, so we need to store the keys locally such
that they will be merged with managed user data when starting sync.

BUG=244472

Review URL: https://codereview.chromium.org/177813003

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253359 0039d316-1c4b-4281-b951-d872f2087c98
Roll trace-viewer deps to r1179

TBR=dsinclair

Review URL: https://codereview.chromium.org/181033002

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253360 0039d316-1c4b-4281-b951-d872f2087c98
Allow MessageFilters to restrict listening to specific message classes

ChannelProxy currently offers messages to all member MessageFilters.  It turns
out that a good portion of the most common message types will never be filtered,
making the O(N) filter walk an unnecessary affair.  To prevent this, allow
MessageFilters to indicate which (if any) subset of message classes they may
filter, allowing the ChannelProxy to refine the list of filters that are offered
a particular message.  This saves ~35us per message received on the browser IO
thread for a typical Android device.

Relanding with a few more guards for MessageFilter removal, access and message
class subscription.

BUG=340881
TBR=asargent@chromium.org

Review URL: https://codereview.chromium.org/142923005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253361 0039d316-1c4b-4281-b951-d872f2087c98
Update .DEPS.git

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@253362 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 253362