Add color enhancer as a chromium accessibility extensions.

Add color enhancer as a chromium accessibility extensions.

BUG=

Committed: https://crrev.com/de13b9b8c461aefcb0a5bd2849d5a800df7babc5
Cr-Commit-Position: refs/heads/master@{#320514}

[Peter Wen, 2015-03-06 19:45:38]

wnwen@chromium.org changed reviewers:
+ kevers@chromium.org, mustaq@chromium.org

[Peter Wen, 2015-03-06 19:45:39]

Please take a look at this import of our code. Primarily converting strings,
modifying the gyp file, and line-length fixes.

Do you guys know how to build these extensions with ninja? :)

[Peter Wen, 2015-03-06 20:51:12]

wnwen@chromium.org changed reviewers:
+ dmazzoni@chromium.org

[Peter Wen, 2015-03-06 20:51:13]

+dmazzoni for import review and OWNERS.

[kevers, 2015-03-09 13:56:59]

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/accessibility_extensions.gyp (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/accessibility_extensions.gyp:105: 'target_name':
'colorenhancer',
Can you please add the GN build change as well.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/common.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:1: // Copyright (c) 2014
The Chromium Authors. All rights reserved.
Please drop (c) here and in other headers.  Also, as this is a new file in the
Chrome codebase, the year should be updated to 2015.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/cvd.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:23: 
Should have jsdoc for all functions.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:79: type_a /*protanomaly*/:
[
jsdoc @emum {string}
Also style for enumeration should be CvdSimulationParams.PROTANOMALY.  I'd
rather not use type_a|b|c as it is less meaningful.  Sorry, I'm being a bit
harsh on the review, but as this is now being moved out of experimental code, it
should follow our strict guidelines.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:115: var
cvdCorrectionMatrices = {
Dead code.  Please remove.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:136: var
cvdCorrectionParams = {
See comments above on enumerations.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:270: console.log(
Please change console.log calls to DebugPrint and add a global var to
enable/disable console debugging (disabled by default).  Alternatively, remove
the console spam if no longer needed.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:287: window.scrollBy(0, 1);
This looks like a strange hack.  Why is it needed?

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/popup.html (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.html:4: <link
rel="stylesheet" type="text/css" href="../res/cvd.css">
We probably should be using widgets in ui/webui/resources for style consistency
with Chrome settings, but can be in a followup CL.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/popup.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:7: function update() {
jsdoc.

Also we have a fair number of global functions here and if cvd.js.  Might be
better to wrap in closures.

[dmazzoni, 2015-03-09 15:40:40]

lgtm

I think you need chromeos=1 in your GYP_DEFINES first, then build
accessibility_extensions with ninja.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/cvd.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:78: var cvdSimulationParams
= {
Could you provide any docs on how these were computed and how someone could
regenerate or reproduce these values?

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:287: window.scrollBy(0, 1);
On 2015/03/09 13:56:59, kevers wrote:
> This looks like a strange hack.  Why is it needed?

Yeah, if the filters don't update without this hack let's file a bug

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/popup.html (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.html:50: <!--
Indicate why commented out. TODO?

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/popup.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:23:
//console.log("updated site " + site + " simulate " + getDefaultSimulate());
Delete commented out code or use log levels?

[kevers, 2015-03-09 15:56:55]

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/cvd.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:78: var cvdSimulationParams
= {
On 2015/03/09 15:40:40, dmazzoni wrote:
> Could you provide any docs on how these were computed and how someone could
> regenerate or reproduce these values?

Peter, these values were generated by doing a polynomial regression on tabulated
values from the following source:
http://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/CVD_Simulation.html.

The full paper can be found here:
http://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/Machado_Oliveira_...


Also feel free to add a TODO(kevers) for unit tests.

[mustaq, 2015-03-09 16:35:18]

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/cvd.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:78: var cvdSimulationParams
= {
On 2015/03/09 15:56:55, kevers wrote:
> On 2015/03/09 15:40:40, dmazzoni wrote:
> > Could you provide any docs on how these were computed and how someone could
> > regenerate or reproduce these values?
> 
> Peter, these values were generated by doing a polynomial regression on
tabulated
> values from the following source:
>
http://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/CVD_Simulation.html.
> 
> The full paper can be found here:
>
http://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/Machado_Oliveira_...
> 
> 
> Also feel free to add a TODO(kevers) for unit tests.

Since we had decided earlier to use severity=1 w/o any UI-triggered
modification, we should replace these 9x3 values into 9 doubles at some point
because
  a*severity^2 + b*severity + c = a+b+c
We should file a bug for this.

[kevers, 2015-03-09 18:41:49]

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/cvd.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:78: var cvdSimulationParams
= {
On 2015/03/09 16:35:18, mustaq wrote:
> On 2015/03/09 15:56:55, kevers wrote:
> > On 2015/03/09 15:40:40, dmazzoni wrote:
> > > Could you provide any docs on how these were computed and how someone
could
> > > regenerate or reproduce these values?
> > 
> > Peter, these values were generated by doing a polynomial regression on
> tabulated
> > values from the following source:
> >
>
http://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/CVD_Simulation.html.
> > 
> > The full paper can be found here:
> >
>
http://www.inf.ufrgs.br/~oliveira/pubs_files/CVD_Simulation/Machado_Oliveira_...
> > 
> > 
> > Also feel free to add a TODO(kevers) for unit tests.
> 
> Since we had decided earlier to use severity=1 w/o any UI-triggered
> modification, we should replace these 9x3 values into 9 doubles at some point
> because
>   a*severity^2 + b*severity + c = a+b+c
> We should file a bug for this.

Thought we decided that we (eventually) wouldn't show the severity slider by
default, but possible that we will still want it under advanced options.  If we
do decide to nuke severity entirely, then the 3x3 matrices for each type of
dichromatic vision can be found in the reference shown above.

[Peter Wen, 2015-03-09 21:35:57]

Thanks for the comments!

@dmazzoni - I still cannot build accessibility_extensions without adding it
manually to src/build/all.gyp. Is there a flag that I need to pass in so the
build system knows about src/u/a/extensions/accessibility_extensions.gyp's
targets?

I am running 'ninja -c out/Release accessibility_extensions' with my gyp
settings in ~/.gyp/include.gypi (which includes chromeos=1, use_goma=1, among
other things, stripping which and regenerating with gclient runhooks did not
seem to affect anything).

PTAL.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/accessibility_extensions.gyp (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/accessibility_extensions.gyp:105: 'target_name':
'colorenhancer',
On 2015/03/09 13:56:59, kevers wrote:
> Can you please add the GN build change as well.

Since there is no current BUILD.gn under accessibility/extensions, one can be
added for all extensions in a follow-up CL tracked separately.

@dmazzoni - is that okay with you?

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/common.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:1: // Copyright (c) 2014
The Chromium Authors. All rights reserved.
On 2015/03/09 13:56:59, kevers wrote:
> Please drop (c) here and in other headers.  Also, as this is a new file in the
> Chrome codebase, the year should be updated to 2015.

Done.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/cvd.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:23: 
On 2015/03/09 13:56:59, kevers wrote:
> Should have jsdoc for all functions.

Added some and others left as TODOs.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:78: var cvdSimulationParams
= {
On 2015/03/09 15:40:40, dmazzoni wrote:
> Could you provide any docs on how these were computed and how someone could
> regenerate or reproduce these values?

Done.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:79: type_a /*protanomaly*/:
[
On 2015/03/09 13:56:59, kevers wrote:
> jsdoc @emum {string}
> Also style for enumeration should be CvdSimulationParams.PROTANOMALY.  I'd
> rather not use type_a|b|c as it is less meaningful.  Sorry, I'm being a bit
> harsh on the review, but as this is now being moved out of experimental code,
it
> should follow our strict guidelines.

Done.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:115: var
cvdCorrectionMatrices = {
On 2015/03/09 13:56:59, kevers wrote:
> Dead code.  Please remove.

Done.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:136: var
cvdCorrectionParams = {
On 2015/03/09 13:56:59, kevers wrote:
> See comments above on enumerations.

Done.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:270: console.log(
On 2015/03/09 13:56:59, kevers wrote:
> Please change console.log calls to DebugPrint and add a global var to
> enable/disable console debugging (disabled by default).  Alternatively, remove
> the console spam if no longer needed.

Do you mean to create a debugPrint global function? I'm not sure what DebugPrint
is.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:287: window.scrollBy(0, 1);
On 2015/03/09 15:40:40, dmazzoni wrote:
> On 2015/03/09 13:56:59, kevers wrote:
> > This looks like a strange hack.  Why is it needed?
> 
> Yeah, if the filters don't update without this hack let's file a bug

Added TODO to investigate.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/popup.html (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.html:4: <link
rel="stylesheet" type="text/css" href="../res/cvd.css">
On 2015/03/09 13:56:59, kevers wrote:
> We probably should be using widgets in ui/webui/resources for style
consistency
> with Chrome settings, but can be in a followup CL.

Added TODO, we should file bugs to track these TODOs later.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.html:50: <!--
On 2015/03/09 15:40:40, dmazzoni wrote:
> Indicate why commented out. TODO?

Done.

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/popup.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:7: function update() {
On 2015/03/09 13:56:59, kevers wrote:
> jsdoc.
> 
> Also we have a fair number of global functions here and if cvd.js.  Might be
> better to wrap in closures.

http://crbug.com/465457

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:23:
//console.log("updated site " + site + " simulate " + getDefaultSimulate());
On 2015/03/09 15:40:40, dmazzoni wrote:
> Delete commented out code or use log levels?

Added TODO as this is part of the next feature (already completed in google3,
just needs to be merged into Chromium after this CL).

[kevers, 2015-03-10 14:07:51]

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/cvd.js (right):

https://codereview.chromium.org/984833004/diff/20001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/cvd.js:270: console.log(
On 2015/03/09 21:35:57, Peter Wen wrote:
> On 2015/03/09 13:56:59, kevers wrote:
> > Please change console.log calls to DebugPrint and add a global var to
> > enable/disable console debugging (disabled by default).  Alternatively,
remove
> > the console spam if no longer needed.
> 
> Do you mean to create a debugPrint global function? I'm not sure what
DebugPrint
> is.

Added a note to clarify in reviewer comment on popup.js.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/background.js (right):

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/background.js:42:
console.log('sending  to ' + siteFromUrl(url) + ' ' +
Please wrap console log in a helper function so that it is visible as console
spam only when debugging.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/common.js (right):

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:29: * The filter should
not apply to these URLs.
@param

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:42: return delta >= 0 &&
delta <= 1;
This method looks overly specialized.  OK with fixing in a followup CL.  We
could achieve the same effect below with a generic clamp(min,max,default)
method.  It could then be used for validating any numeric value.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:108: function
validSeverity(severity) {
See note above for validDelta.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:174: var DEFAULT_TYPE =
'PROTANOMALY';
Less error prone to use an enumeration. i.e.:

/**
 * @enum {string}
 */
 var CvdType = {
    PROTANOMALY, 'PROTANOMALY'
    ...
 };

This way we get a javascript error if there is a typo in the name rather than
hitting an unexpected conditional. the method validType then becomes

validType(type) {
  return type in CvdType;
}

Naturally, we would want a shared enum across js files.  This change can be in a
followup CL.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/popup.js (right):

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:14: getSiteDelta(site) +
',' + getSiteSeverity(site));
Please wrap console.log output so that it only appears when debugging. e.g.

// Set to true when debugging.
enableDebugPrint = false;

function DebugPrint(message) {
  if (enableDebugPrint) {
    console.log(message);
  }
}

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:36: * Callback for color
rotation slider.
@param here and below.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:106: // TODO(mustaq):
Finish simulate feature.
Do we want the simulate feature in the color enhancer extension or only in dev
tools?

[Peter Wen, 2015-03-10 19:00:56]

PTAL. :)

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/background.js (right):

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/background.js:42:
console.log('sending  to ' + siteFromUrl(url) + ' ' +
On 2015/03/10 14:07:51, kevers wrote:
> Please wrap console log in a helper function so that it is visible as console
> spam only when debugging.

Done.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/common.js (right):

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:29: * The filter should
not apply to these URLs.
On 2015/03/10 14:07:51, kevers wrote:
> @param

Done.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:42: return delta >= 0 &&
delta <= 1;
On 2015/03/10 14:07:51, kevers wrote:
> This method looks overly specialized.  OK with fixing in a followup CL.  We
> could achieve the same effect below with a generic clamp(min,max,default)
> method.  It could then be used for validating any numeric value.

Acknowledged.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:108: function
validSeverity(severity) {
On 2015/03/10 14:07:51, kevers wrote:
> See note above for validDelta.

Agreed, quite a bit of this storage code can be DRY'ed. :)

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/common.js:174: var DEFAULT_TYPE =
'PROTANOMALY';
On 2015/03/10 14:07:51, kevers wrote:
> Less error prone to use an enumeration. i.e.:
> 
> /**
>  * @enum {string}
>  */
>  var CvdType = {
>     PROTANOMALY, 'PROTANOMALY'
>     ...
>  };
> 
> This way we get a javascript error if there is a typo in the name rather than
> hitting an unexpected conditional. the method validType then becomes
> 
> validType(type) {
>   return type in CvdType;
> }
> 
> Naturally, we would want a shared enum across js files.  This change can be in
a
> followup CL.

Agreed. Added TODO.

In Chrome 42 we can do
var otherEnum = {
  [CvdType.PROTANOMALY]: data,
}

https://www.chromestatus.com/feature/4873630588600320

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
File ui/accessibility/extensions/colorenhancer/src/popup.js (right):

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:14: getSiteDelta(site) +
',' + getSiteSeverity(site));
On 2015/03/10 14:07:51, kevers wrote:
> Please wrap console.log output so that it only appears when debugging. e.g.
> 
> // Set to true when debugging.
> enableDebugPrint = false;
> 
> function DebugPrint(message) {
>   if (enableDebugPrint) {
>     console.log(message);
>   }
> }

I changed it so we automatically enable logging for debugging (unpacked
extension) and turn it off for production (crx from webstore).

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:36: * Callback for color
rotation slider.
On 2015/03/10 14:07:51, kevers wrote:
> @param here and below.

Done.

https://codereview.chromium.org/984833004/diff/40001/ui/accessibility/extensi...
ui/accessibility/extensions/colorenhancer/src/popup.js:106: // TODO(mustaq):
Finish simulate feature.
On 2015/03/10 14:07:51, kevers wrote:
> Do we want the simulate feature in the color enhancer extension or only in dev
> tools?

Originally yes, but we thought it would be beneficial to have it visible and
tested in the extension before integrating into dev tools.

[kevers, 2015-03-13 15:40:31]

Awesome.  Like your implementation of debugPrint.
LGTM.

[Peter Wen, 2015-03-13 16:26:22]

The CQ bit was checked by wnwen@chromium.org

[Peter Wen, 2015-03-13 16:26:22]

The patchset sent to the CQ was uploaded after l-g-t-m from
dmazzoni@chromium.org
Link to the patchset: https://codereview.chromium.org/984833004/#ps60001 (title:
"More docs.")

[commit-bot: I haz the power, 2015-03-13 16:26:46]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/984833004/60001

[commit-bot: I haz the power, 2015-03-13 16:56:55]

Committed patchset #4 (id:60001)

[commit-bot: I haz the power, 2015-03-13 16:57:51]

Patchset 4 (id:??) landed as
https://crrev.com/de13b9b8c461aefcb0a5bd2849d5a800df7babc5
Cr-Commit-Position: refs/heads/master@{#320514}