Refine StorageMonitor storage device getter

Refine StorageMonitor storage device getter 

This fix is to rename GetAttachedStorage to GetAttachedRemovableStorages for
better understanding, and add GetAllAvailableStorages method to allow the
consumers of StorageMonitor to query all available storages on the system,
including fixed and removable storages.

TEST=unit_tests --gtest_filter=StorageMonitorTest.*

[Hongbo Min, 2013-05-29 06:35:36]

vandebo@, as follow-up of https://codereview.chromium.org/15896007/, I create
this separate CL for GetAllAvailableStorages adding.

One thing I need to double-check is, is GetAttachedStorage desigend to only
return removable storages, since I rename it to GetAttachedRemovableStorages.

[Lei Zhang, 2013-05-29 10:03:32]

Platform specific concerns:
- Mac: do you consider DMGs as attached storages?
- Linux: ditto, for loopback mounts.
- CrOS: I still think you are not getting all the storages.

Overall design:
- For removable storages, we have a centralized map in StorageMonitor that the
platform-specific impls feed into.
- The new code you are adding reaches into the platform-specific impls to fetch
the data instead.

https://codereview.chromium.org/16186002/diff/2001/chrome/browser/storage_mon...
File chrome/browser/storage_monitor/storage_monitor.cc (right):

https://codereview.chromium.org/16186002/diff/2001/chrome/browser/storage_mon...
chrome/browser/storage_monitor/storage_monitor.cc:65: // Returns empty vector as
default implemenation.
typo, add NOTIMPLEMENTED()

[wrong vandebo, 2013-05-29 15:16:16]

https://codereview.chromium.org/16186002/diff/2001/chrome/browser/storage_mon...
File chrome/browser/storage_monitor/storage_monitor.h (right):

https://codereview.chromium.org/16186002/diff/2001/chrome/browser/storage_mon...
chrome/browser/storage_monitor/storage_monitor.h:105: // Returns the meta
information for all available storages on the system,
We probably don't want to introduce a second method here.  We should just update
the description, name, and callers of the existing method.  StorageInfo contains
enough information to tell you if it is removable or not.

[Greg Billock, 2013-05-29 17:58:19]

https://codereview.chromium.org/16186002/diff/2001/chrome/browser/storage_mon...
File chrome/browser/storage_monitor/storage_monitor.h (right):

https://codereview.chromium.org/16186002/diff/2001/chrome/browser/storage_mon...
chrome/browser/storage_monitor/storage_monitor.h:105: // Returns the meta
information for all available storages on the system,
On 2013/05/29 15:16:16, vandebo1 wrote:
> We probably don't want to introduce a second method here.  We should just
update
> the description, name, and callers of the existing method.  StorageInfo
contains
> enough information to tell you if it is removable or not.

We've discussed making the method return all known storages, instead of just
removable ones, and I think that is something we want to do. We need to get them
at this point, anyway.

[Hongbo Min, 2013-05-30 02:24:29]

On 2013/05/29 10:03:32, Lei Zhang wrote:
> Platform specific concerns:
> - Mac: do you consider DMGs as attached storages?

I am not expertized at Mac, I found the |disk_info_map_| in StorageMonitorMac
contains all interested storages. 

> - Linux: ditto, for loopback mounts.

The loopback mount on linux is treated as an "fixed" type storage according to
the MtabWatcherLinux implementation.

> - CrOS: I still think you are not getting all the storages.

If not all storages are taken into consideration, then is there any criteria to
choose the specific storages for CrOS.


> 
> Overall design:
> - For removable storages, we have a centralized map in StorageMonitor that the
> platform-specific impls feed into.
> - The new code you are adding reaches into the platform-specific impls to
fetch
> the data instead.
>

[Hongbo Min, 2013-05-30 02:29:40]

On 2013/05/29 17:58:19, Greg Billock wrote:
>
https://codereview.chromium.org/16186002/diff/2001/chrome/browser/storage_mon...
> File chrome/browser/storage_monitor/storage_monitor.h (right):
> 
>
https://codereview.chromium.org/16186002/diff/2001/chrome/browser/storage_mon...
> chrome/browser/storage_monitor/storage_monitor.h:105: // Returns the meta
> information for all available storages on the system,
> On 2013/05/29 15:16:16, vandebo1 wrote:
> > We probably don't want to introduce a second method here.  We should just
> update
> > the description, name, and callers of the existing method.  StorageInfo
> contains
> > enough information to tell you if it is removable or not.
> 
> We've discussed making the method return all known storages, instead of just
> removable ones, and I think that is something we want to do. We need to get
them
> at this point, anyway.

The platform-specific concerns from thestig@ push me to think more about the
StorageMonitor. Take Linux for example, the storage list is retrieved from
/etc/mtab file, and as we all know, the mount point can also be umounted even
for fixed storage devices, and more we won't get attachment/detachment
notification caused by fixed storage devices mounting/unmounting although
/etc/mtab gets changed.

In that sense, how do we define a clear meaning for "removable" world in
StorageMonitor and systemInfo.storage API?

[Hongbo Min, 2013-06-03 01:30:32]

Close this CL since Haojian will take over this CL at
https://codereview.chromium.org/15988011/. Thanks.