Add a BuildFlag annotation, which when specified for classes, will wrap
generated code in `#ifdef` or `#ifndef` blocks. This functionality is
used for conditionally excluding generated code when NIghtly becomes
Beta, without the need to regenerate bindings.
MozReview-Commit-ID: L2NFM8CHKqF
Currently, when we generate JNI wrapper for an inner class, the
resulting C++ class will not actually be a nested class of the enclosing
class. As a result, the class can be confusing to use. For example,
wrapping Java class GeckoThread.State results in two unrelated C++
classes, GeckoThread and State, and it'd be confusing to use State by
itself.
This patch adds support for inner classes. We start by scanning only for
top-level classes, and when processing each top-level class, we
recursively scan for inner classes through
JarClassIterator.getInnerClasses() and CodeGenerator.generateClasses().
For each Java inner classes, the resulting C++ class will be a nested
class. For example, wrapping GeckoThread.State will produce
widget::GeckoThread and widget::GeckoThread::State.
