NaCl-Chrome integration

This is a copy of http://codereview.chromium.org/153002/show
First step towards NaCl-Chrome integration:1. NaCl plugin becomes a built-in plugin in Chrome and runs in the renderer process.2. Most of the changes are related to launching the NaCl process (that loads and runs the NaCl module) and establishing the initial communication between that process and the NaCl plugin.3. This CL relies on another CL that contains the changes on the Native Client side: http://codereview.chromium.org/1501904. Command line flag "--internal-nacl" is required to enable the built-in NaCl plugin.5. NaCl still cannot run in Chrome sandbox, so the "--no-sandbox" flag is also required

TBR=bradnelson


Committed: http://src.chromium.org/viewvc/chrome?view=rev&revision=26540