The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/72e4521766dcfa34cef6500ff43ae33075978c6b

commit 72e4521766dcfa34cef6500ff43ae33075978c6b
Author: Dmitry Skiba <dskiba@chromium.org>
Date: Fri May 18 19:11:34 2018

Trace generated JNI functions.

This CL modifies jni_generator to add TRACE_EVENTs to generated
functions when "enable_jni_tracing" GN flag is set to "true".

Tracing events are added as TRACE_EVENT0("jni", <name>), where
<name> is the fully qualified name of the function that is about
to be called. I.e. <name> can be either Java or C++ function name,
depending on the direction of the call. Example:

package com.example;

@JNINamespace("com_example")
public class Foo {
    @CalledByNative
    Foo();
    // TRACE_EVENT0("jni", "com.example.Foo.<init>")

    @CalledByNative
    void callbackFromNative();
    // TRACE_EVENT0("jni", "com.example.Foo.callbackFromNative")

    native void nativeInstanceMethod(long nativeInstance);
    // TRACE_EVENT0("jni", "com_example::Foo::InstanceMethod")

    static native void nativeStaticMethod();
    // TRACE_EVENT0("jni", "com_example::JNI_Foo_StaticMethod")
}

Bug:  842241 
Change-Id: Ib110a7070e3d2de05c2090055fb4acc8a6b40e78
Reviewed-on: https://chromium-review.googlesource.com/1064705
Reviewed-by: agrieve <agrieve@chromium.org>
Commit-Queue: Dmitry Skiba <dskiba@chromium.org>
Cr-Commit-Position: refs/heads/master@{#559983}
[modify] https://crrev.com/72e4521766dcfa34cef6500ff43ae33075978c6b/base/android/jni_generator/jni_generator.py
[modify] https://crrev.com/72e4521766dcfa34cef6500ff43ae33075978c6b/base/android/jni_generator/jni_generator_helper.h
[modify] https://crrev.com/72e4521766dcfa34cef6500ff43ae33075978c6b/base/android/jni_generator/jni_generator_tests.py
[add] https://crrev.com/72e4521766dcfa34cef6500ff43ae33075978c6b/base/android/jni_generator/testTracing.golden
[modify] https://crrev.com/72e4521766dcfa34cef6500ff43ae33075978c6b/build/config/android/rules.gni