VectorComparer should check null.

VectorComparer should check null.

We use VectorComparer to compare WTF::Vector<T>.
If T is not primitive type, we use std::equal to compare.
By the way, we use the WTF::VectorBufferBase class for a base class of Vector.  VectorBufferBase doesn't alloc a array if we init it without a size argument.
As a conclusion, we pass NULL object to std::equal when we compare Vectors with the default constructor.
It is asserted especially on a Windows debug build.

BUG=

Committed: https://src.chromium.org/viewvc/blink?view=rev&revision=176189

[tkent, 2014-06-16 04:42:26]

https://codereview.chromium.org/332113002/diff/1/Source/wtf/Vector.h
File Source/wtf/Vector.h (right):

https://codereview.chromium.org/332113002/diff/1/Source/wtf/Vector.h#newcode227
Source/wtf/Vector.h:227: if (!a || !b) {
I recommend to write popular case at first.  e.g.

if (LIKELY(a && b))
    return std::equal(...);
return !a && !b;

https://codereview.chromium.org/332113002/diff/1/Source/wtf/VectorTest.cpp
File Source/wtf/VectorTest.cpp (right):

https://codereview.chromium.org/332113002/diff/1/Source/wtf/VectorTest.cpp#ne...
Source/wtf/VectorTest.cpp:294: EXPECT_TRUE(vector1 == vector2);
More test cases.
 - LHS has internal buffer, RHS has no.
 - LHS has no internal buffer, RHS has.

[yoichio, 2014-06-16 04:58:45]

https://codereview.chromium.org/332113002/diff/1/Source/wtf/Vector.h
File Source/wtf/Vector.h (right):

https://codereview.chromium.org/332113002/diff/1/Source/wtf/Vector.h#newcode227
Source/wtf/Vector.h:227: if (!a || !b) {
On 2014/06/16 04:42:26, tkent wrote:
> I recommend to write popular case at first.  e.g.
> 
> if (LIKELY(a && b))
>     return std::equal(...);
> return !a && !b;

Done.

https://codereview.chromium.org/332113002/diff/1/Source/wtf/VectorTest.cpp
File Source/wtf/VectorTest.cpp (right):

https://codereview.chromium.org/332113002/diff/1/Source/wtf/VectorTest.cpp#ne...
Source/wtf/VectorTest.cpp:294: EXPECT_TRUE(vector1 == vector2);
On 2014/06/16 04:42:26, tkent wrote:
> More test cases.
>  - LHS has internal buffer, RHS has no.
>  - LHS has no internal buffer, RHS has.

Done.

[tkent, 2014-06-16 05:01:53]

lgtm

[commit-bot: I haz the power, 2014-06-16 05:02:14]

CQ is trying da patch. Follow status at
 https://chromium-status.appspot.com/cq/yoichio@chromium.org/332113002/20001

[commit-bot: I haz the power, 2014-06-16 08:48:45]

Change committed as 176189