Native resource leak due to the missing pthread_detach call in mozc::Thread::Detach

[yukawa]

(This issue was originally reported by @besthust as #340)

Environment

• Mozc 2.17.2313.102 and prior
• Android 6.0.1 MMB29S / Nexus 5 2013.

How to setup the environment to reproduce.

python build_mozc.py build -c Debug package
adb install -r -d android/bin/MozcForAndroid-debug.apk
adb shell ime set org.mozc.android.inputmethod.japanese/.MozcService

Steps to reproduce

1. adb shell dumpsys meminfo org.mozc.android.inputmethod.japanese
2. Tap the search box on the home screen.
3. Tap the buck button to dismiss the software keyboard.
4. Return to the step 1.

Expected behavior

• In the step 1 the native heap size should be stable for each iteration.

Actual behavior

• In the step 1 the native heap size keeps growing for each iteration.

Additional information

This is a native resource (including memory) leak due to the missing pthread_detach call in mozc::Thread::Detach src/base/thread.cc

void Thread::Detach() {
  state_->handle_.reset(nullptr);
}

Possible affected platforms:

• Mozc for Android
• Mozc for Linux
• Mozc for NaCl
• Mozc for OS X

Internal Issue ID: 26499803.