Selectively perform JNI registration in render processes on Android.

base/android/jni_generator/jni_generator.py

Index: base/android/jni_generator/jni_generator.py
diff --git a/base/android/jni_generator/jni_generator.py b/base/android/jni_generator/jni_generator.py
index 0173a2c1172e0bf21de939fb3cd0e6fcae86e311..3241622a6cad09d1ea64f363bb6096c570fd2b48 100755
--- a/base/android/jni_generator/jni_generator.py
+++ b/base/android/jni_generator/jni_generator.py
@@ -632,10 +632,9 @@ class JNIFromJavaP(object):
         self.constant_fields.append(
             ConstantField(name=match.group('name'),
                           value=value.group('value')))
-
     self.inl_header_file_generator = InlHeaderFileGenerator(
-        self.namespace, self.fully_qualified_class, [],
-        self.called_by_natives, self.constant_fields, options)
+        self.namespace, self.fully_qualified_class, [], self.called_by_natives,
+        self.constant_fields, options)
 
   def GetContent(self):
     return self.inl_header_file_generator.GetContent()
@@ -669,12 +668,13 @@ class JNIFromJavaSource(object):
     jni_namespace = ExtractJNINamespace(contents) or options.namespace
     natives = ExtractNatives(contents, options.ptr_type)
     called_by_natives = ExtractCalledByNatives(contents)
+    maindex = '@MainDex' in contents

[Torne, 2016/12/14 11:40:24]

The other Extract* functions are doing more than just searching for a substring
match; several of them are already recognising annotations I think? Is there a
better way to do this than just looking for a substring?

     if len(natives) == 0 and len(called_by_natives) == 0:
       raise SyntaxError('Unable to find any JNI methods for %s.' %
                         fully_qualified_class)
     inl_header_file_generator = InlHeaderFileGenerator(
-        jni_namespace, fully_qualified_class, natives, called_by_natives,
-        [], options)
+        jni_namespace, fully_qualified_class, natives, called_by_natives, [],
+        options, maindex)
     self.content = inl_header_file_generator.GetContent()
 
   @classmethod
@@ -710,7 +710,7 @@ class InlHeaderFileGenerator(object):
   """Generates an inline header file for JNI integration."""
 
   def __init__(self, namespace, fully_qualified_class, natives,
-               called_by_natives, constant_fields, options):
+               called_by_natives, constant_fields, options, maindex=False):
     self.namespace = namespace
     self.fully_qualified_class = fully_qualified_class
     self.class_name = self.fully_qualified_class.split('/')[-1]
@@ -718,6 +718,7 @@ class InlHeaderFileGenerator(object):
     self.called_by_natives = called_by_natives
     self.header_guard = fully_qualified_class.replace('/', '_') + '_JNI'
     self.constant_fields = constant_fields
+    self.maindex = maindex
     self.options = options
 
 
@@ -864,6 +865,15 @@ ${NATIVES}
       early_exit = """\
   if (base::android::IsManualJniRegistrationDisabled()) return true;
 """
+    if not self.maindex:
+      early_exit += """\
+  base::android::LibraryProcessType proc_type =

[Torne, 2016/12/14 11:40:24]

Can you put this in jni_generator_helper.h as an inline function or something?
The logic here probably shouldn't be hardcoded in the generator itself - the
generator just needs to make the "main dex or not" call.

Maybe something like "RegisterMainDexClassesOnly()"?

+      base::android::GetLibraryProcessType(env);

[Torne, 2016/12/14 11:40:24]

GetLibraryProcessType is a JNI call; if we're going to hit it a bunch of times
in startup like this then we should probably explicitly store it in native
instead.

+  if (proc_type != base::android::PROCESS_BROWSER &&
+      proc_type != base::android::PROCESS_UNINITIALIZED) {

[Torne, 2016/12/14 11:40:25]

Is there really a case where the process type is unitialized? Can we not just
crash at an earlier point if it's not set, instead of trying to make it safe?

+    return true;
+  }
+"""
 
     values = {'REGISTER_NATIVES_SIGNATURE': signature,
               'EARLY_EXIT': early_exit,