Add support for generation of header files and registration of proxy native methods.

'Proxy' native methods are declared in an @JniStaticNatives interface without a native
qualifier and indicate that the JNI annotation processor should generate code
to link between the equivalent native method as if it were declare statically.
Under the hood the annotation processor generates the actual native
method declaration in another another class (org.chromium.base.natives.GEN_JNI)
but generates wrapper code so it can be called through the declaring class.

This CL adds support to the python header generator to generate header files and
registration header files for native methods declared in an @JniStaticNatives
annotated interface which uses the JNI annotation processor.

Change-Id: I7a1c10f67d6b7c7dad3423634bdb995e76e751a4
Bug: 898261
Reviewed-on: https://chromium-review.googlesource.com/c/1297184
Commit-Queue: Aiden Benner <abenner@google.com>
Reviewed-by: agrieve <agrieve@chromium.org>
Reviewed-by: Eric Stevenson <estevenson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#603900}
12 files changed