WIP: Migrate Wiki content over to src/docs

docs/linux_chromium_arm.md

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+Note this currently contains various recipes:
+
+
+
+---
+
+
+# Recipe1: Building for an ARM CrOS device
+This recipe uses `ninja` (instead of `make`) so its startup time is much lower (sub-1s, instead of tens of seconds), is integrated with goma (for google-internal users) for very high parallelism, and uses `sshfs` instead of `scp` to significantly speed up the compile-run cycle.  It has moved to https://sites.google.com/a/chromium.org/dev/developers/how-tos/-quickly-building-for-cros-arm-x64 (mostly b/c of the ease of attaching files to sites).
+
+
+
+---
+
+
+# Recipe2: Explicit Cross compiling
+
+Due to the lack of ARM hardware with the grunt to build Chromium native, cross compiling is currently the recommended method of building for ARM.
+
+These instruction are designed to run on Ubuntu Precise.
+
+### Installing the toolchain
+
+The install-build-deps script can be used to install all the compiler
+and library dependencies directly from Ubuntu:
+
+```
+$ ./build/install-build-deps.sh --arm
+```
+
+### Installing the rootfs
+
+A prebuilt rootfs image is kept up-to-date on Cloud Storage.  It will
+automatically be installed by gclient runhooks installed if you have 'target\_arch=arm' in your GYP\_DEFINES.
+
+To install the sysroot manually you can run:
+```
+$ ./chrome/installer/linux/sysroot_scripts/install-debian.wheezy.sysroot.py --arch=arm
+```
+
+### Building
+
+To build for ARM, using the clang binary in the chrome tree, use the following settings:
+
+```
+export GYP_CROSSCOMPILE=1
+export GYP_DEFINES="target_arch=arm"
+```
+
+There variables need to be set at gyp-time (when you run gyp\_chromium),
+but are not needed at build-time (when you run make/ninja).
+
+## Testing
+
+### Automated Build and Testing
+
+Chromium's testing infrastructure for ARM/Linux is (to say the least)
+in its infancy.  There are currently two builders setup, one on the
+FYI waterfall and one the the trybot waterfall:
+
+http://build.chromium.org/p/chromium.fyi/builders/Linux%20ARM%20Cross-Compile
+http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_arm
+
+
+These builders cross compile on x86-64 and then trigger testing
+on real ARM hard bots:
+
+http://build.chromium.org/p/chromium.fyi/builders/Linux%20ARM%20Tests%20%28Panda%29/
+http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_arm_tester
+
+Unfortunately, even those the builders are usually green, the testers
+are not yet well maintained or monitored.
+
+There is compile-only trybot and fyi bot also:
+
+http://build.chromium.org/p/chromium.fyi/builders/Linux%20ARM
+http://build.chromium.org/p/tryserver.chromium.linux/builders/linux_arm_compile
+
+### Testing with QEMU
+
+If you don't have a real ARM machine, you can test with QEMU. For instance, there are some prebuilt QEMU Debian images here: http://people.debian.org/~aurel32/qemu/.  Another option is to use the rootfs generated by rootstock, as mentioned above.
+
+Here's a minimal xorg.conf if needed:
+
+```
+Section "InputDevice"
+        Identifier      "Generic Keyboard"
+        Driver          "kbd"
+        Option          "XkbRules"      "xorg"
+        Option          "XkbModel"      "pc105"
+        Option          "XkbLayout"     "us"
+EndSection
+
+Section "InputDevice"
+        Identifier      "Configured Mouse"
+        Driver          "mouse"
+EndSection
+
+Section "Device"
+        Identifier      "Configured Video Device"
+        Driver  "fbdev"
+        Option          "UseFBDev"              "true"
+EndSection
+
+Section "Monitor"
+        Identifier      "Configured Monitor"
+EndSection
+
+Section "Screen"
+        Identifier      "Default Screen"
+        Monitor         "Configured Monitor"
+        Device          "Configured Video Device"
+        DefaultDepth 8
+        SubSection "Display"
+            Depth 8
+            Modes "1024x768" "800x600" "640x480"
+        EndSubSection
+EndSection
+```
+
+### Notes
+  * To building for thumb reduces the stripped release binary by around 9MB, equating to ~33% of the binary size.  To enable thumb, set 'arm\_thumb': 1
+  * TCmalloc does not have an ARM port, so it is disabled.