CamelCase TransformOperation::OperationType enums

This is just a straightforward renaming of the TransformOperation enum
OperationType to match the current style guide.

BUG=

Review URL: https://chromiumcodereview.appspot.com/22366002

git-svn-id: svn://svn.chromium.org/blink/trunk@155591 bbb929c8-8fbe-4397-9dbb-9b2b20218538