[clang] Use -Wshorten-64-to-32 to enable warnings about 64bit to 32bit truncations.

[clang] Use -Wshorten-64-to-32 to enable warnings about 64bit to 32bit truncations.

Currently only the Win64 bots report this warnings, which adds quite
some overhead to the development process. With this flag we also get
compiler warnings about implicit 64bit to 32bit truncations when
building with clang on Linux/x64 and Mac/x64.

R=svenpanne@chromium.org

Committed: https://crrev.com/4486c47d9b207e95f15598135262bb43f0c5dc00
Cr-Commit-Position: refs/heads/master@{#28093}

[Benedikt Meurer, 2015-04-28 05:40:13]

Sven: This adds the compiler flag and fixes all invalid 64bit to 32bit
truncations detected by clang (mostly in non-Windows code, since the Win64
compiler already complained about the ones in shared code). Also removed the
MemoryMappedFile duplication on POSIX platforms. Please take a look.

Ben: FYI

[Benedikt Meurer, 2015-04-28 06:06:44]

Rodolph: Maybe you can look into enabling this warning for arm64 as well. It
gives a bunch of warnings in the arm64/ directory that are related to mixing int
and int64_t.

[Sven Panne, 2015-04-28 06:47:55]

The CQ bit was checked by svenpanne@chromium.org

[Sven Panne, 2015-04-28 06:47:56]

lgtm

[commit-bot: I haz the power, 2015-04-28 06:48:00]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1111733002/80001

[commit-bot: I haz the power, 2015-04-28 06:54:13]

Committed patchset #5 (id:80001)

[commit-bot: I haz the power, 2015-04-28 06:54:25]

Patchset 5 (id:??) landed as
https://crrev.com/4486c47d9b207e95f15598135262bb43f0c5dc00
Cr-Commit-Position: refs/heads/master@{#28093}

[Rodolph Perfetta, 2015-04-28 10:54:28]

On 2015/04/28 06:06:44, Benedikt Meurer wrote:
> Rodolph: Maybe you can look into enabling this warning for arm64 as well. It
> gives a bunch of warnings in the arm64/ directory that are related to mixing
int
> and int64_t.

We are looking into it.