base: Add three helper functions to Values API.

base: Add three helper functions to Values API.

Added three new helper functions to simplify the usage of the API by the clients.

So now they are able to say:

- base::NullValue() instead of base::Value::CreateNullValue();

- base::TrueValue() instead of base::Value::CreateBooleanValue(true); and new base::FundamentalValue(true);

- base::FalseValue() instead of base::Value::CreateBooleanValue(false); and new base::FundamentalValue(false);

Advantages:
- This is shorter than the other forms, easy to read and much less verbose.

BUG=None
TEST=base_unittests --gtest_filter=Values*

R=evan@chromium.org

[tfarina, 2011-08-16 02:52:54]

Hi Evan, please take a look.

The interesting changes are in base/values.*

The rest is just search and replace adjusting the callers.

This is a simplified version of http://codereview.chromium.org/7649006/

Thanks!

[tfarina, 2011-08-18 00:00:44]

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