Update the build instructions to be consistent.

docs/android_build_instructions.md

Index: docs/android_build_instructions.md
diff --git a/docs/android_build_instructions.md b/docs/android_build_instructions.md
index b188f4b03bddad730d6acb0a035d57266b07bd9d..cc9d42a177b7393724ce11506cb66d54cb863982 100644
--- a/docs/android_build_instructions.md
+++ b/docs/android_build_instructions.md
@@ -1,99 +1,96 @@
 # Android Build Instructions
 
+**See also [the old version of this page](old_android_build_instructions.md).**
+
+Google employee? See [go/building-chrome](https://goto.google.com/building-chrome) instead.
+
 [TOC]
 
-## Prerequisites
+## System requirements
 
-A Linux build machine capable of building [Chrome for
-Linux](https://chromium.googlesource.com/chromium/src/+/master/docs/linux_build_instructions_prerequisites.md).
-Other (Mac/Windows) platforms are not supported for Android.
+* A 64-bit Intel machine running Linux with at least 8GB of RAM. More
+  than 16GB is highly recommended.
+* At least 100GB of free disk space.
+* You must have Git and Python installed already.
 
-## Getting the code
+Most development is done on Ubuntu. Other distros may or may not work;
+see the [linux instructions](linux_build_instructions.md) for some suggestions.
 
-First, check out and install the [depot\_tools
-package](https://commondatastorage.googleapis.com/chrome-infra-docs/flat/depot_tools/docs/html/depot_tools_tutorial.html#_setting_up).
+Building the Android client on Windows or Mac is not supported and doesn't work.
 
-Then, if you have no existing checkout, create your source directory and
-get the code:
+## Install `depot_tools`
 
-```shell
-mkdir ~/chromium && cd ~/chromium
-fetch --nohooks android # This will take 30 minutes on a fast connection
-```
+Clone the depot_tools repository:
 
-If you have an existing Linux checkout, you can add Android support by
-appending `target_os = ['android']` to your .gclient file (in the
-directory above src):
+    $ git clone https://chromium.googlesource.com/chromium/tools/depot_tools.git
 
-```shell
-cat > .gclient <<EOF
- solutions = [ ...existing stuff in here... ]
- target_os = [ 'android' ] # Add this to get Android stuff checked out.
-EOF
-```
+Add depot_tools to the end of your PATH (you will probably want to put this
+in your ~/.bashrc or ~/.zshrc). Assuming you cloned depot_tools
+to /path/to/depot_tools:
 
-Then run gclient sync to get the Android stuff checked out:
+    $ export PATH=$PATH:/path/to/depot_tools
 
-```shell
-gclient sync
-```
+## Get the code
 
-## (Optional) Check out LKGR
+Create a chromium directory for the checkout and change to it (you can call
+this whatever you like and put it wherever you like, as
+long as the full path has no spaces):
 
-If you want a single build of Chromium in a known good state, sync to
-the LKGR ("last known good revision"). You can find it
-[here](http://chromium-status.appspot.com/lkgr), and the last 100
-[here](http://chromium-status.appspot.com/revisions). Run:
+    $ mkdir ~/chromium && cd ~/chromium
+    $ fetch --nohooks android
 
-```shell
-gclient sync --nohooks -r <lkgr-sha1>
-```
+If you don't want the full repo history, you can save a lot of time by
+adding the `--no-history` flag to fetch.
 
-This is not needed for a typical developer workflow; only for one-time
-builds of Chromium.
+Expect the command to take 30 minutes on even a fast connection, and many
+hours on slower ones.
 
-## Configure GN
+If you've already installed the build dependencies on the machine (from another
+checkout, for example), you can omit the `--nohooks` flag and fetch
+will automatically execute `gclient runhooks` at the end.
 
-Create a build directory and set the build flags with:
+When fetch completes, it will have created a directory called `src`.
+The remaining instructions assume you are now in that directory:
 
-```shell
-gn args out/Default
-```
+    $ cd src
 
- You can replace out/Default with another name you choose inside the out
-directory.
+### Converting an existing Linux checkout
 
-Also be aware that some scripts (e.g. tombstones.py, adb_gdb.py)
-require you to set `CHROMIUM_OUTPUT_DIR=out/Default`.
+If you have an existing Linux checkout, you can add Android support by
+appending `target_os = ['android']` to your .gclient file (in the
+directory above src):
 
-This command will bring up your editor with the GN build args. In this
-file add:
+    $ echo "target_os = [ 'android' ]" >> ../.gclient
 
-```
-target_os = "android"
-target_cpu = "arm"  # (default)
-is_debug = true  # (default)
-
-# Other args you may want to set:
-is_component_build = true
-is_clang = true
-symbol_level = 1  # Faster build with fewer symbols. -g1 rather than -g2
-enable_incremental_javac = true  # Much faster; experimental
-```
+Then run gclient sync to pull the new Android dependencies:
 
-You can also specify `target_cpu` values of "x86" and "mipsel". Re-run
-gn args on that directory to edit the flags in the future. See the [GN
-build
-configuration](https://www.chromium.org/developers/gn-build-configuration)
-page for other flags you may want to set.
+    gclient sync
 
-### Install build dependencies
+(This is actually the difference between `fetch android` and `fetch chromium`).
 
-Update the system packages required to build by running:
+### Install additional build dependencies
 
-```shell
-./build/install-build-deps-android.sh
-```
+Once you have checked out the code, run
+
+    build/install-build-deps-android.sh
+
+to get all of the dependencies you need to build on Linux *plus* all of the
+Android-specific dependencies (you need some of the regular Linux dependencies
+because an Android build builds a bunch of the Linux tools and utilities).
+
+### Run the hooks
+
+Once you've run `install-build-deps` at least once, you can now run the
+chromium-specific hooks, which will download additional binaries and other
+things you might need:
+
+    $ gclient runhooks
+
+*Optional*: You can also [install API keys](https://www.chromium.org/developers/how-tos/api-keys)
+if you want to talk to some of the Google services, but this is not necessary
+for most development and testing purposes.
+
+### Configure the JDK
 
 Make also sure that OpenJDK 1.7 is selected as default:
 
@@ -104,13 +101,40 @@ Make also sure that OpenJDK 1.7 is selected as default:
 `sudo update-alternatives --config jar`
 `sudo update-alternatives --config jarsigner`
 
-### Synchronize sub-directories.
+## Setting up the Build
 
-```shell
-gclient sync
-```
+Chromium uses [Ninja](https://ninja-build.org) as its main build tool, and
+a tool called [GN](../tools/gn/docs/quick_start.md) to generate
+the .ninja files to do the build. To create a build directory configured
+to build Android, run:
+
+    $ gn gen '--args="target_os="android"' out/Default
+
+* You only have to do run this command once, it will self-update the build
+  files as needed after that.
+* You can replace `out/Default` with another directory name, but we recommend
+  it should still be a subdirectory of `out`.
+* To specify build parameters for GN builds, including release settings,
+  see [GN build configuration](https://www.chromium.org/developers/gn-build-configuration). 
+  The default will be a debug component build matching the current host
+  operating system and CPU.
+* For more info on GN, run `gn help` on the command line or read the
+  [quick start guide](../tools/gn/docs/quick_start.md).
+
+Also be aware that some scripts (e.g. tombstones.py, adb_gdb.py)
+require you to set `CHROMIUM_OUTPUT_DIR=out/Default`.
+
+## Build Chromium
+
+Build Chromium with Ninja using the command:
+
+    $ ninja -C out/Default chrome_public_apk
 
-## Build and install the APKs
+You can get a list of all of the other build targets from GN by running
+`gn ls out/Default` from the command line. To compile one, pass to Ninja
+the GN label with no preceding "//" (so for `//chrome/test:unit_tests`
+use ninja -C out/Default chrome/test:unit_tests`).
+## Installing and Running Chromium on a device
 
 If the `adb_install_apk.py` script below fails, make sure aapt is in
 your PATH. If not, add aapt's path to your PATH environment variable (it
@@ -290,9 +314,9 @@ To uninstall:
 out/Default/bin/install_chrome_public_apk_incremental -v --uninstall
 ```
 
-### Miscellaneous
+## Tips, tricks, and troubleshooting
 
-#### Rebuilding libchrome.so for a particular release
+### Rebuilding libchrome.so for a particular release
 
 These instructions are only necessary for Chrome 51 and earlier.