To pave the way for making it possible to support both manual JNI function registration and native JNI exports in the same build, improve the implementation of native JNI exports by: 1) using a symbol alias instead of a wrapper function to give the standard Java exported name to non-method native functions. The previous implementation depended on the function in the .cc file being inlined into the wrapper function to avoid an extra indirection, which will not be possible if both modes are supported at once since there will be a reference to the real function in the manual registration table and thus it must exist. 2) marking the global used for the Java class reference as potentially unused, as it's not guaranteed to be referenced if there are no @CalledByNative Java functions and native exports are being used. This wasn't causing a problem before as the downstream WebView build doesn't have unused variable warnings enabled, but was preventing upstream usage of native export mode. No functional changes are intended. BUG=442327 Review URL: https://codereview.chromium.org/841063003 Cr-Commit-Position: refs/heads/master@{#310568}