android: Realign stack pointer on JNI entry.

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 428c4939ae82c879dcf8f4c146c1deab21c33a9e..f115b45f33ff467aa77486c4a964855aa0c6da29 100755
--- a/base/android/jni_generator/jni_generator.py
+++ b/base/android/jni_generator/jni_generator.py
@@ -1030,8 +1030,14 @@ ${NATIVES}
           'PARAM0_NAME': native.params[0].name,
           'P0_TYPE': native.p0_type,
       })
+      # Dalvik JIT generated code doesn't guarantee 16-byte stack alignment on
+      # x86 - use force_align_arg_pointer to realign the stack at the JNI
+      # boundary. crbug.com/655248
       template = Template("""\
 extern "C" __attribute__((visibility("default")))
+#if defined(ARCH_CPU_X86)
+__attribute__((force_align_arg_pointer))
+#endif
 ${RETURN} ${STUB_NAME}(JNIEnv* env,
     ${PARAMS_IN_STUB}) {
   ${PROFILING_ENTERED_NATIVE}
@@ -1045,6 +1051,9 @@ ${RETURN} ${STUB_NAME}(JNIEnv* env,
 static ${RETURN_DECLARATION} ${NAME}(JNIEnv* env, ${PARAMS});
 
 extern "C" __attribute__((visibility("default")))
+#if defined(ARCH_CPU_X86)
+__attribute__((force_align_arg_pointer))
+#endif
 ${RETURN} ${STUB_NAME}(JNIEnv* env, ${PARAMS_IN_STUB}) {
   ${PROFILING_ENTERED_NATIVE}
   return ${NAME}(${PARAMS_IN_CALL})${POST_CALL};