Selectively perform JNI registration in render processes on Android.

chrome/browser/android/chrome_entry_point.cc

Index: chrome/browser/android/chrome_entry_point.cc
diff --git a/chrome/browser/android/chrome_entry_point.cc b/chrome/browser/android/chrome_entry_point.cc
index 5bc9215ded3a07c1f0967cfd1f5461d7ffd50081..4a540518ea52b1de61bebefb9d50edf12251fa6c 100644
--- a/chrome/browser/android/chrome_entry_point.cc
+++ b/chrome/browser/android/chrome_entry_point.cc
@@ -3,6 +3,7 @@
 // found in the LICENSE file.
 
 #include "base/android/jni_android.h"
+#include "base/android/jni_utils.h"
 #include "base/android/library_loader/library_loader_hooks.h"
 #include "base/bind.h"
 #include "chrome/app/android/chrome_jni_onload.h"
@@ -25,6 +26,15 @@ bool NativeInit() {
 
 // This is called by the VM when the shared library is first loaded.
 JNI_EXPORT jint JNI_OnLoad(JavaVM* vm, void* reserved) {
+  // By default, all JNI methods are registered. However, since render processes
+  // don't need very much Java code, we enable selective JNI registration on the
+  // Java side and only register a subset of JNI methods.
+  base::android::InitVM(vm);

[Ted C, 2017/01/31 17:56:54]

why do we need this InitVM here?  Wondering why the ordering is different from
the monochrome entry point?

[Torne, 2017/01/31 18:04:50]

You need to call InitVM before AttachCurrentThread works, and the
SetJniRegistrationType here is conditional on something that needs that. It'd be
fine for monochrome to do it in the same order, though.

[estevenson, 2017/01/31 18:56:41]

Yeah, we need JNIEnv for making calls to Java. I think this currently gets
called here for regular Chrome
(https://cs.chromium.org/chromium/src/base/android/base_jni_onload.cc?q=base_j...)
- we need to leave that regardless for places where tests call
base::android::OnJNIOnLoadRegisterJNI directly.

Changed the order of monochrome_entry_point to match chrome_entry_point.

+  JNIEnv* env = base::android::AttachCurrentThread();
+  if (base::android::isSelectiveJniRegistrationEnabled(env)) {
+    base::android::SetJniRegistrationType(
+        base::android::SELECTIVE_JNI_REGISTRATION);
+  }
   if (!android::OnJNIOnLoadRegisterJNI(vm, base::Bind(&RegisterJNI))) {
     return -1;
   }