Cast int to SkScalar in SkCanvas

The motivation for this changeset is to fix the following build failure in google3-

third_party/skia/src/core/SkCanvas.cpp:1711:61: error: non-constant-expression cannot be narrowed from type 'int32_t' (aka 'int') to 'SkScalar' (aka 'float') in initializer list [-Wc++11-narrowing]
        0, SkIntToScalar(c.fLeft), SkIntToScalar(c.fRight), w
                                                            ^
third_party/skia/src/core/SkCanvas.cpp:1711:61: note: override this message by inserting an explicit cast
        0, SkIntToScalar(c.fLeft), SkIntToScalar(c.fRight), w
                                                            ^
                                                            static_cast<SkScalar>( )
Committed: https://code.google.com/p/skia/source/detail?r=6979

[reed1, 2013-01-02 22:01:51]

lgtm

[epoger, 2013-01-03 18:32:36]

LGTM