In SkWriter32::writeString, initialize all memory reserved.

In SkWriter32::writeString, initialize all memory reserved.

SkFlatData compares data which is sometimes created by writeString.
Initialize all the memory in writeString so it does not compare
uninitialized memory.

See http://code.google.com/p/skia/issues/detail?id=721&thanks=721

Committed: https://code.google.com/p/skia/source/detail?r=4715

[reed1, 2012-07-20 15:18:23]

seems good.

can we write a unittest that exercises this?

1. write some bit pattern to the write-buffer
2. writestring("a", "ab", "abc", "abcd", "abcde", ...)
3. assert that the align4() of the string len is always 0 padded

[Leon, 2012-07-20 17:38:43]

On 2012/07/20 15:18:23, reed1 wrote:
> seems good.
> 
> can we write a unittest that exercises this?
> 
> 1. write some bit pattern to the write-buffer
> 2. writestring("a", "ab", "abc", "abcd", "abcde", ...)
> 3. assert that the align4() of the string len is always 0 padded

Done.

[reed1, 2012-07-20 17:53:28]

https://codereview.appspot.com/6428054/diff/4001/tests/Writer32Test.cpp
File tests/Writer32Test.cpp (right):

https://codereview.appspot.com/6428054/diff/4001/tests/Writer32Test.cpp#newco...
tests/Writer32Test.cpp:71: 
Do we want to explicitly write some non-zero pattern into storage, before we
call writeString, so we're sure we don't accidentally pass the new asserts?

[Leon, 2012-07-20 18:47:03]

https://codereview.appspot.com/6428054/diff/4001/tests/Writer32Test.cpp
File tests/Writer32Test.cpp (right):

https://codereview.appspot.com/6428054/diff/4001/tests/Writer32Test.cpp#newco...
tests/Writer32Test.cpp:71: 
On 2012/07/20 17:53:28, reed1 wrote:
> Do we want to explicitly write some non-zero pattern into storage, before we
> call writeString, so we're sure we don't accidentally pass the new asserts?

I do not think writing a pattern into storage would be meaningful, since
writer->flatten() will replace it with whatever the writer has (the problem I'm
fixing is that "what the writer has" was uninitialized). I think it would be
more interesting to write a non-zero pattern into the writer's memory. That is
doable if the initial storage is large enough, but in the case where space needs
to be allocated I do not see a way to put any particular pattern there and then
write over it (unless we override new?).

[reed1, 2012-07-20 20:22:43]

lgtm