Move all static constants in dtoa/cached-powers.* to .rodata section

Move all static constants in dtoa/cached-powers.* from .data section to
.rodata. This was done by marking those as const and hardcoding their
values instead of computing them. Runtime assertions were added to make
sure the hardcoded values are correct and kept up-to-date.

This data can now be shared between different library instances on
Android, thus saving RAM.

The size of non-shareable .data in wtf/dtoa/wtf.cached-powers.o went from 1424
bytes to 0 byte. The size of shareable .rodata went from 760 bytes to 2520
bytes.

BUG=249746

Review URL: https://codereview.chromium.org/48833002

git-svn-id: svn://svn.chromium.org/blink/trunk@161250 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Add a walk() method to filesystem forwarding to os.walk

This method will be used in a bunch of follow-up CLs that locate breakpad minidumps,

BUG=none
R=mkwst@chromium.org

Review URL: https://codereview.chromium.org/51353007

git-svn-id: svn://svn.chromium.org/blink/trunk@161251 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Remove dead code in RenderLayerCompositor

reasonsForCompositing() is dead code after we removed the logging code
from RenderLayerCompositor. The name and semantics are overloaded with
other functions and the implementation is actually not quite right,
anyway. So, let's just remove it.

Review URL: https://codereview.chromium.org/51943005

git-svn-id: svn://svn.chromium.org/blink/trunk@161252 bbb929c8-8fbe-4397-9dbb-9b2b20218538