Add const version of toText(), and use it.

We'd like to avoid bare static_cast.

BUG=none
TEST=none; no behavior changes.

Review URL: https://chromiumcodereview.appspot.com/23658029

git-svn-id: svn://svn.chromium.org/blink/trunk@157501 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Use the CPU() and COMPILER() macros for audio where it is applicable.

Review URL: https://chromiumcodereview.appspot.com/23936006

git-svn-id: svn://svn.chromium.org/blink/trunk@157502 bbb929c8-8fbe-4397-9dbb-9b2b20218538