Remove unnecesary usage of RefPtr and PassRefPtr of DatabaseContext.

Remove unnecesary usage of RefPtr and PassRefPtr of DatabaseContext.

This is a preparation to move DatabaseContext to Oilpan heap.

We don't need to use RefPtr/PassRefPtr of DatabaseContext for function arguments
and function return value. They don't move ownership of DatabaseContext. They
might be meaningful if we didn't have self->ref() in DatabaseContext::create.

Also, this CL simplifies DatabaseContext::backend, and makes
DatabaseManager::databaseContextFor private.

BUG=347902
TEST=none; no behavior changes.

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=170020

[tkent, 2014-03-26 04:41:18]

Please review this.

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
File Source/modules/webdatabase/DatabaseManager.cpp (left):

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
Source/modules/webdatabase/DatabaseManager.cpp:114: return
databaseContext.release();
This code block is exactly equivalent to "return
PassRefPtr<DatabaseContext>(m_contextMap.get(context));"

[kouhei (in TOK), 2014-03-26 04:45:44]

On 2014/03/26 04:41:18, tkent wrote:
> Please review this.
> 
>
https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
> File Source/modules/webdatabase/DatabaseManager.cpp (left):
> 
>
https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
> Source/modules/webdatabase/DatabaseManager.cpp:114: return
> databaseContext.release();
> This code block is exactly equivalent to "return
> PassRefPtr<DatabaseContext>(m_contextMap.get(context));"

lgtm

[tkent, 2014-03-26 04:52:21]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2014-03-26 04:52:25]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tkent@chromium.org/209043008/1

[haraken, 2014-03-26 04:57:24]

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
File Source/modules/webdatabase/DatabaseManager.cpp (left):

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
Source/modules/webdatabase/DatabaseManager.cpp:114: return
databaseContext.release();
On 2014/03/26 04:41:18, tkent wrote:
> This code block is exactly equivalent to "return
> PassRefPtr<DatabaseContext>(m_contextMap.get(context));"

I don't fully understand this.

  RefPtr<DatabaseContext> databaseContext = adoptRef(m_contextMap.get(context));
  return databaseContext.release();

will be equivalent to:

  return
PassRefPtr<DatabaseContext>(m_contextMap.get(context));

On the other hand,

  RefPtr<DatabaseContext> databaseContext = adoptRef(m_contextMap.get(context));
  if (databaseContext)
    databaseContext->ref();
  return databaseContext.release();

won't be equivalent to:

  return
PassRefPtr<DatabaseContext>(m_contextMap.get(context));

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
File Source/modules/webdatabase/DatabaseManager.cpp (right):

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
Source/modules/webdatabase/DatabaseManager.cpp:111: // DataabseContext::create.

Typo: DatabaseContext::create

[tkent, 2014-03-26 05:15:46]

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
File Source/modules/webdatabase/DatabaseManager.cpp (left):

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
Source/modules/webdatabase/DatabaseManager.cpp:114: return
databaseContext.release();
On 2014/03/26 04:57:24, haraken wrote:
> On 2014/03/26 04:41:18, tkent wrote:
> > This code block is exactly equivalent to "return
> > PassRefPtr<DatabaseContext>(m_contextMap.get(context));"
> 
> I don't fully understand this.
> 
>   RefPtr<DatabaseContext> databaseContext =
adoptRef(m_contextMap.get(context));
>   return databaseContext.release();
> 
> will be equivalent to:
> 
>   return
> PassRefPtr<DatabaseContext>(m_contextMap.get(context));

No.  the former is equivalent to just adoptRef(...), which doesn't update the
reference counter.  PassRefPtr<T>(T*) increments the reference counter.

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
File Source/modules/webdatabase/DatabaseManager.cpp (right):

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
Source/modules/webdatabase/DatabaseManager.cpp:111: // DataabseContext::create.
On 2014/03/26 04:57:24, haraken wrote:
> 
> Typo: DatabaseContext::create

Will fix in the next CL.

[commit-bot: I haz the power, 2014-03-26 05:33:32]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2014-03-26 05:33:32]

List of reviewers changed. haraken@chromium.org did a drive-by without LGTM'ing!

[tkent, 2014-03-26 05:36:29]

The CQ bit was checked by tkent@chromium.org

[commit-bot: I haz the power, 2014-03-26 05:36:40]

CQ is trying da patch. Follow status at
https://chromium-status.appspot.com/cq/tkent@chromium.org/209043008/1

[commit-bot: I haz the power, 2014-03-26 05:37:15]

Change committed as 170020

[haraken, 2014-03-26 05:37:50]

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
File Source/modules/webdatabase/DatabaseManager.cpp (left):

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
Source/modules/webdatabase/DatabaseManager.cpp:114: return
databaseContext.release();
On 2014/03/26 05:15:46, tkent wrote:
> On 2014/03/26 04:57:24, haraken wrote:
> > On 2014/03/26 04:41:18, tkent wrote:
> > > This code block is exactly equivalent to "return
> > > PassRefPtr<DatabaseContext>(m_contextMap.get(context));"
> > 
> > I don't fully understand this.
> > 
> >   RefPtr<DatabaseContext> databaseContext =
> adoptRef(m_contextMap.get(context));
> >   return databaseContext.release();
> > 
> > will be equivalent to:
> > 
> >   return
> > PassRefPtr<DatabaseContext>(m_contextMap.get(context));
> 
> No.  the former is equivalent to just adoptRef(...), which doesn't update the
> reference counter.  PassRefPtr<T>(T*) increments the reference counter.

sorry, I don't yet get it.

PassRefPtr<Foo> func1() {
  RefPtr<Foo> foo = adoptRef(new Foo()); // refcount becomes 1.
  return foo.release(); // refcount stays 1.
}

void func2() {
  RefPtr<Foo> foo = func1();  // refcount stays 1.
}

PassRefPtr<Foo> func3() {
  Foo* foo = new Foo(); // refcount is 0.
  return PassRefPtr<Foo>(foo); // refcount becomes 1.
}

void func4() {
  RefPtr<Foo> foo = func3();  // refcount stays 1.
}

Given the above:

  RefPtr<Foo> foo = adoptRef(new Foo());
  return foo.release();

is equivalent to:

  return PassRefPtr<Foo>(new Foo());

Am I missing something?

[tkent, 2014-03-26 05:50:20]

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
File Source/modules/webdatabase/DatabaseManager.cpp (left):

https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
Source/modules/webdatabase/DatabaseManager.cpp:114: return
databaseContext.release();
> sorry, I don't yet get it.
> 
> PassRefPtr<Foo> func1() {
>   RefPtr<Foo> foo = adoptRef(new Foo()); // refcount becomes 1.
>   return foo.release(); // refcount stays 1.
> }

> 
> void func2() {
>   RefPtr<Foo> foo = func1();  // refcount stays 1.
> }
> 
> PassRefPtr<Foo> func3() {
>   Foo* foo = new Foo(); // refcount is 0.
>   return PassRefPtr<Foo>(foo); // refcount becomes 1.
> }

Incorrect.
new Foo() creates a Foo with m_refCount==1.
PassRefPtr<Foo>(foo) makes m_refCount 2.

> void func4() {
>   RefPtr<Foo> foo = func3();  // refcount stays 1.
> }

So, m_refCount will be 2.

[haraken, 2014-03-26 05:55:37]

On 2014/03/26 05:50:20, tkent wrote:
>
https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
> File Source/modules/webdatabase/DatabaseManager.cpp (left):
> 
>
https://codereview.chromium.org/209043008/diff/1/Source/modules/webdatabase/D...
> Source/modules/webdatabase/DatabaseManager.cpp:114: return
> databaseContext.release();
> > sorry, I don't yet get it.
> > 
> > PassRefPtr<Foo> func1() {
> >   RefPtr<Foo> foo = adoptRef(new Foo()); // refcount becomes 1.
> >   return foo.release(); // refcount stays 1.
> > }
> 
> > 
> > void func2() {
> >   RefPtr<Foo> foo = func1();  // refcount stays 1.
> > }
> > 
> > PassRefPtr<Foo> func3() {
> >   Foo* foo = new Foo(); // refcount is 0.
> >   return PassRefPtr<Foo>(foo); // refcount becomes 1.
> > }
> 
> Incorrect.
> new Foo() creates a Foo with m_refCount==1.
> PassRefPtr<Foo>(foo) makes m_refCount 2.
> 
> > void func4() {
> >   RefPtr<Foo> foo = func3();  // refcount stays 1.
> > }
> 
> So, m_refCount will be 2.

ah, makes sense. Sorry about the noise.

[haraken, 2014-03-26 05:55:45]

LGTM