Use readability.js for page distillation

This change updates dom_distiller to use the readability.js script
for page distillation.

BUG=288015

Review URL: https://codereview.chromium.org/62233004

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235540 0039d316-1c4b-4281-b951-d872f2087c98
Pass retry_task to SyncScheduler::ScheduleConfiguration

Pass retry_task through ConfigurationParams to
SyncScheduler::ScheduleConfiguration. We might in the future do
configuration asynchronously and passing retry_task through asynchronous
calls will be handy.

SyncManagerTestWithMockScheduler.ConfigurationRetry is no longer needed,
SyncSchedulerTest.ConfigWithBackingOff tests this functionality.

BUG=259913

Review URL: https://codereview.chromium.org/62283011

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235541 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235541
cleanup: Replace usage of chrome::AddBlankTabAt with chrome::AddTabAt().

BUG=319011
R=sky@chromium.org

Review URL: https://codereview.chromium.org/73503007

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235542 0039d316-1c4b-4281-b951-d872f2087c98
This CL implements the Asynchronous Module Definition (AMD)
API, which we plan to use for JavaScript in Mojo. We don't
yet implement every feature in the AMD spec
<https://github.com/amdjs/amdjs-api/wiki/AMD>, but we
implement the basic framework, which will let us get started
writing and testing JavaScript modules in Mojo.

The two other leading choices for a modules system are
CommonJS and ES6 modules. We decided not to use CommonJS,
despite its popularity, because it implies the ability to
load modules synchronously. That works well in server
environments like node.js, but it won't work well for Mojo
where modules might be loaded across a network.

I would really like to have used ES6 modules, but the spec
isn't finalized yet and V8 doesn't yet implement them. It's
likely that we'll replace this AMD module system with ES6
modules once ES6 modules are ready.

Structurally, I've implemented AMD in the ModuleRegistry
class in a new "modules" directory in Gin.  Nothing else in
Gin (except the tests) depends on ModuleRegistry, which
means folks are free to use Gin without AMD.  At the Mojo
layer, I've added a dependency on AMD.

BUG=317398

Review URL: https://codereview.chromium.org/62333018

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@235543 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 235543