WIP: Migrate Wiki content over to src/docs

docs/profiling_content_shell_on_android.md

+# Introduction
+
+Below are the instructions for setting up profiling for Content Shell on Android. This will let you generate profiles for ContentShell. This will require linux, building an userdebug Android build, and wiping the device.
+
+## Prepare your device.
+
+You need an Android 4.2+ device (Galaxy Nexus, Nexus 4, 7, 10, etc.) which you don’t mind erasing all data, rooting, and installing a userdebug build on.
+
+## Get and build content\_shell\_apk for Android
+(These instructions have been carefully distilled from http://code.google.com/p/chromium/wiki/AndroidBuildInstructions)
+
+  1. Get the code! You’ll want a second checkout as this will be android-specific. You know the drill: http://dev.chromium.org/developers/how-tos/get-the-code
+  1. Append this to your .gclient file: `target_os = ['android']`
+  1. Create `chromium.gyp_env` next to your .gclient file: `echo "{ 'GYP_DEFINES': 'OS=android', }" > chromium.gyp_env`
+  1. (Note: All these scripts assume you’re using "bash" (default) as your shell.)
+  1. Sync and runhooks (be careful not to run hooks on the first sync):
+```
+gclient sync --nohooks
+. build/android/envsetup.sh
+gclient runhooks
+```
+  1. No need to install any API Keys.
+  1. Install Oracle’s Java: http://goo.gl/uPRSq. Grab the appropriate x64 .bin file, `chmod +x`, and then execute to extract. You then move that extracted tree into /usr/lib/jvm/, rename it java-6-sun and set:
+```
+export JAVA_HOME=/usr/lib/jvm/java-6-sun
+export ANDROID_JAVA_HOME=/usr/lib/jvm/java-6-sun
+```
+  1. Type ‘`java -version`’ and make sure it says java version "1.6.0\_35” without any mention of openjdk before proceeding.
+  1. `sudo build/install-build-deps-android.sh`
+  1. Time to build!
+```
+ninja -C out/Release content_shell_apk
+```
+
+## Setup the physical device
+
+> Plug in your device. Make sure you can talk to your device, try "`adb shell ls`"
+
+## Root your device and install a userdebug build
+
+  1. This may require building your own version of Android: http://source.android.com/source/building-devices.html
+  1. A build that works is: manta / android-4.2.2\_r1 or master /       full\_manta-userdebug.
+
+## Root your device
+  1. Run `adb root`. Every time you connect your device you’ll want to run this.
+  1. If adb is not available, make sure to run “`. build/android/envsetup.sh`”
+> If you get the error “error: device offline”, you may need to become a  developer on your device before Linux will see it. On Jellybean 4.2.1 and above this requires going to “about phone” or “about tablet” and clicking the build number 7 times: http://androidmuscle.com/how-to-enable-usb-debugging-developer-options-on-nexus-4-and-android-4-2-devices/
+
+## Run a Telemetry perf profiler
+
+You can run any Telemetry benchmark with --profiler=perf, and it will:
+1) Download "perf" and "perfhost"
+2) Install on your device
+3) Run the test
+4) Setup symlinks to work with the --symfs parameter
+
+
+You can also run "manual" tests with Telemetry, more information here:
+http://www.chromium.org/developers/telemetry/profiling#TOC-Manual-Profiling---Android
+
+The following steps describe building "perf", which is no longer necessary if you use Telemetry.
+
+
+## Install /system/bin/perf on your device (not needed for Telemetry)
+
+```
+# From inside the android source tree (not inside Chromium)
+mmm external/linux-tools-perf/
+adb remount # (allows you to write to the system image)
+adb sync
+adb shell perf top # check that perf can get samples (don’t expect symbols) 
+```
+
+## Enable profiling
+> Rebuild content\_shell\_apk with profiling enabled
+```
+export GYP_DEFINES="$GYP_DEFINES profiling=1"
+build/gyp_chromium
+ninja -C out/Release content_shell_apk
+```
+## Install ContentShell
+> Install with the following:
+```
+build/android/adb_install_apk.py --apk out/Release/apks/ContentShell.apk --apk_package org.chromium.content_shell
+```
+
+## Run ContentShell
+> Run with the following:
+```
+./build/android/adb_run_content_shell
+```
+> If content\_shell “stopped unexpectedly” use “`adb logcat`” to debug.  If you see ResourceExtractor exceptions, a clean build is your solution.  crbug.com/164220
+
+## Setup a “symbols” directory with symbols from your build (not needed for Telemetry)
+  1. Figure out exactly what path content\_shell\_apk (or chrome, etc) installs to.
+    * On the device, navigate ContentShell to about:crash
+```
+adb logcat | grep libcontent_shell_content_view.so
+```
+> > You should find a path that’s something like /data/app-lib/org.chromium.content\_shell-1/libcontent\_shell\_content\_view.so
+  1. Make a symbols directory
+```
+mkdir symbols (this guide assumes you put this next to src/)
+```
+  1. Make a symlink from your symbols directory to your un-stripped content\_shell.
+```
+mkdir -p symbols/data/app-lib/org.chromium.content_shell-1 (or whatever path in app-lib you got above)
+ln -s `pwd`/src/out/Release/lib/libcontent_shell_content_view.so `pwd`/symbols/data/app-lib/org.chromium.content_shell-1
+```
+
+## Install perfhost\_linux locally (not needed for Telemetry)
+
+
+> Note: modern versions of perf may also be able to process the perf.data files from the device.
+  1. perfhost\_linux can be built from: https://android.googlesource.com/platform/external/linux-tools-perf/.
+  1. Place perfhost\_linux next to symbols, src, etc.
+```
+chmod a+x perfhost_linux
+```
+
+## Actually record a profile on the device!
+> Run the following:
+```
+adb shell ps | grep content (look for the pid of the sandboxed_process)
+adb shell perf record -g -p 12345 sleep 5
+adb pull /data/perf.data
+```
+
+## Create the report
+  1. Run the following:
+```
+./perfhost_linux report -g -i perf.data --symfs symbols/
+```
+  1. If you don’t see chromium/webkit symbols, make sure that you built/pushed Release, and that the symlink you created to the .so is valid!
+  1. If you have symbols, but your callstacks are nonsense, make sure you ran build/gyp\_chromium after setting profiling=1, and rebuilt.
+
+## Add symbols for the kernel
+  1. By default, /proc/kallsyms returns 0 for all symbols, to fix this, set “/proc/sys/kernel/kptr\_restrict” to 0:
+```
+adb shell echo “0” > /proc/sys/kernel/kptr_restrict
+```
+  1. See http://lwn.net/Articles/420403/ for explanation of what this does.
+```
+adb pull /proc/kallsyms symbols/kallsyms
+```
+  1. Now add --kallsyms to your perfhost\_linux command:
+```
+./perfhost_linux report -g -i perf.data --symfs symbols/ --kallsyms=symbols/kallsyms
+```