Add a new GetInstance() method for singleton classes, take 2.

Add a new GetInstance() method for singleton classes, take 2.

This is a small step towards making all singleton classes use the Singleton<T> pattern within their code and not expect the callers to know about it. 

This CL includes all files except those under chrome/browser, chrome/net, chrome/service and third_party/WebKit (these will be done in future CLs).

Suggested files to focus for reviewers:
- joi@ for files under src/ceee
- tommi@ for files under src/chrome_frame
- maruel@ for the rest of the files.

BUG=65298
TEST=all existing tests should continue to pass.

Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=68577

[M-A Ruel, 2010-12-07 17:32:20]

Also, once there's no appearance of Singleton in headers files, you could add a
check in src/PRESUBMIT.py so
singleton.h cannot be included from another header file.

http://codereview.chromium.org/5581008/diff/2001/base/global_descriptors_posix.h
File base/global_descriptors_posix.h (right):

http://codereview.chromium.org/5581008/diff/2001/base/global_descriptors_posi...
base/global_descriptors_posix.h:45: static GlobalDescriptors* GetInstance();
You realize that you're creating two objects here? Why not just use the Leaky
one? The other one is for unit tests? If so, just put one of them in #if
defined(UNIT_TEST)

[Satish, 2010-12-07 17:45:27]

> Also, once there's no appearance of Singleton in headers files, you could add
a
> check in src/PRESUBMIT.py so
> singleton.h cannot be included from another header file.

I plan to add a presubmit check for disallowing the string "Singleton<" in the
header files. But singleton.h will still be allowed in headers because a lot of
places in the code use it and forward declaring the singleton traits in every
single header which uses it seems ugly (and needs to be updated if say the
default traits changed in future).

http://codereview.chromium.org/5581008/diff/2001/base/global_descriptors_posix.h
File base/global_descriptors_posix.h (right):

http://codereview.chromium.org/5581008/diff/2001/base/global_descriptors_posi...
base/global_descriptors_posix.h:45: static GlobalDescriptors* GetInstance();
On 2010/12/07 17:32:21, Marc-Antoine Ruel wrote:
> You realize that you're creating two objects here? Why not just use the Leaky
> one? The other one is for unit tests? If so, just put one of them in #if
> defined(UNIT_TEST)

The leaky instance is created in src/chrome/app/chrome_main:LowLevelInit() for
mac and linux, so that lives through the lifetime of the app. In addition to
this various places in the code create the GlobalDescriptors singleton with
default traits. I have not modified this behavior as it looks to be done
intentionally, instead just added these 2 methods to wrap around them.

[M-A Ruel, 2010-12-07 17:49:17]

lgtm for the rest, just make sure Evan is fine about the dual singleton for
GlobalDescriptors.

http://codereview.chromium.org/5581008/diff/2001/base/global_descriptors_posix.h
File base/global_descriptors_posix.h (right):

http://codereview.chromium.org/5581008/diff/2001/base/global_descriptors_posi...
base/global_descriptors_posix.h:45: static GlobalDescriptors* GetInstance();
On 2010/12/07 17:45:27, Satish wrote:
> On 2010/12/07 17:32:21, Marc-Antoine Ruel wrote:
> > You realize that you're creating two objects here? Why not just use the
Leaky
> > one? The other one is for unit tests? If so, just put one of them in #if
> > defined(UNIT_TEST)
> 
> The leaky instance is created in src/chrome/app/chrome_main:LowLevelInit() for
> mac and linux, so that lives through the lifetime of the app. In addition to
> this various places in the code create the GlobalDescriptors singleton with
> default traits. I have not modified this behavior as it looks to be done
> intentionally, instead just added these 2 methods to wrap around them.

Ok, adding Evan to know if it was intentional.

[Evan Martin, 2010-12-07 17:55:16]

http://codereview.chromium.org/5581008/diff/2001/base/global_descriptors_posix.h
File base/global_descriptors_posix.h (right):

http://codereview.chromium.org/5581008/diff/2001/base/global_descriptors_posi...
base/global_descriptors_posix.h:45: static GlobalDescriptors* GetInstance();
On 2010/12/07 17:49:17, Marc-Antoine Ruel wrote:
> On 2010/12/07 17:45:27, Satish wrote:
> > On 2010/12/07 17:32:21, Marc-Antoine Ruel wrote:
> > > You realize that you're creating two objects here? Why not just use the
> Leaky
> > > one? The other one is for unit tests? If so, just put one of them in #if
> > > defined(UNIT_TEST)
> > 
> > The leaky instance is created in src/chrome/app/chrome_main:LowLevelInit()
for
> > mac and linux, so that lives through the lifetime of the app. In addition to
> > this various places in the code create the GlobalDescriptors singleton with
> > default traits. I have not modified this behavior as it looks to be done
> > intentionally, instead just added these 2 methods to wrap around them.
> 
> Ok, adding Evan to know if it was intentional.

Ugh, no, this was definitely not intentional.  :(
Please let me fix the mess, and don't propagate it here.

[Satish, 2010-12-07 17:59:05]

> Ugh, no, this was definitely not intentional.  :(
> Please let me fix the mess, and don't propagate it here.

Would you like me to fix it as part of this CL? What is the intended usage?

[Evan Martin, 2010-12-07 18:00:46]

On Tue, Dec 7, 2010 at 9:59 AM,  <satish@chromium.org> wrote:
>> Ugh, no, this was definitely not intentional.  :(
>> Please let me fix the mess, and don't propagate it here.
>
> Would you like me to fix it as part of this CL? What is the intended usage?

It should be different, since it's an unrelated problem.  I'll send you a CL.

[tommi (sloooow) - chröme, 2010-12-07 18:38:17]

lgtm for chrome frame.

[Jói, 2010-12-07 18:56:25]

LGTM for CEEE.

Please run ceee/smoke_test.bat in an admin command prompt before submitting to
make sure the CEEE tests pass.

Very cool stuff, thanks for doing this Satish.