Google Native Client allows for executing native C/C++ code within a web-browser using sandboxing and software-based fault isolation. Native Client is a big component to Chrome and Chrome OS, but even while being open-source it hasn't been adopted outside of Google's web world. Google has supported NaCl on x86 and x86_64 while the ARM support has been in-development for nearly three years.
The Native Client released yesterday has full support for ARM devices with version 25 and onwards. Details can be found on the Chromium Blog.
Coming out later this year is Portable Native Client, Google's next-generation version of NaCl. Portable Native Client will be architecture-independent by using LLVM bit-code that is then translated to the respective architecture's machine code at run-time, among other benefits by heavily leveraging LLVM.