Enable optimize max for arm in GN + update docs

docs/getting_started.md

 # Getting Started
 
 How to get and build the libyuv code.
 
 ## Pre-requisites
 
 You'll need to have depot tools installed: https://www.chromium.org/developers/how-tos/install-depot-tools
 Refer to chromium instructions for each platform for other prerequisites.
 
 ## Getting the Code
 
 Create a working directory, enter it, and run:
 
     gclient config https://chromium.googlesource.com/libyuv/libyuv
     gclient sync
 
-
 Then you'll get a .gclient file like:
 
     solutions = [
       { "name"        : "libyuv",
         "url"         : "https://chromium.googlesource.com/libyuv/libyuv",
         "deps_file"   : "DEPS",
         "managed"     : True,
         "custom_deps" : {
         },
         "safesync_url": "",
       },
     ];
 
-
 For iOS add `;target_os=['ios'];` to your OSX .gclient and run `GYP_DEFINES="OS=ios" gclient sync.`
 
 Browse the Git reprository: https://chromium.googlesource.com/libyuv/libyuv/+/master
 
 ### Android
 For Android add `;target_os=['android'];` to your Linux .gclient
 
-
     solutions = [
       { "name"        : "libyuv",
         "url"         : "https://chromium.googlesource.com/libyuv/libyuv",
         "deps_file"   : "DEPS",
         "managed"     : True,
         "custom_deps" : {
         },
         "safesync_url": "",
       },
     ];
@@ skipping 16 matching lines @@
 
 To get just the source (not buildable):
 
     git clone https://chromium.googlesource.com/libyuv/libyuv
 
 
 ## Building the Library and Unittests
 
 ### Windows
 
-    set GYP_DEFINES=target_arch=ia32
-    call python gyp_libyuv -fninja -G msvs_version=2013
-    ninja -j7 -C out\Release
-    ninja -j7 -C out\Debug
+    call gn gen out/Release "--args=is_debug=false target_cpu=\"x86\""
+    call gn gen out/Debug "--args=is_debug=true target_cpu=\"x86\""
+    ninja -j7 -v -C out/Release
+    ninja -j7 -v -C out/Debug
 
-    set GYP_DEFINES=target_arch=x64
-    call python gyp_libyuv -fninja -G msvs_version=2013
-    ninja -C out\Debug_x64
-    ninja -C out\Release_x64
+    call gn gen out/Release "--args=is_debug=false target_cpu=\"x64\""
+    call gn gen out/Debug "--args=is_debug=true target_cpu=\"x64\""
+    ninja -j7 -v -C out/Release
+    ninja -j7 -v -C out/Debug
 
-#### Building with clangcl
+#### Building with clang-cl
+
     set GYP_DEFINES=clang=1 target_arch=ia32
     call python tools\clang\scripts\update.py
-    call python gyp_libyuv -fninja libyuv_test.gyp
-    ninja -C out\Debug
-    ninja -C out\Release
 
-### OSX
+    call gn gen out/Release "--args=is_debug=false is_official_build=false is_clang=true target_cpu=\"x86\""
+    call gn gen out/Debug "--args=is_debug=true is_official_build=false is_clang=true target_cpu=\"x86\""
+    ninja -j7 -v -C out/Release
+    ninja -j7 -v -C out/Debug
 
-Clang 64 bit shown. Remove `clang=1` for GCC and change x64 to ia32 for 32 bit.
+    call gn gen out/Release "--args=is_debug=false is_official_build=false is_clang=true target_cpu=\"x64\""
+    call gn gen out/Debug "--args=is_debug=true is_official_build=false is_clang=true target_cpu=\"x64\""
+    ninja -j7 -v -C out/Release
+    ninja -j7 -v -C out/Debug
 
-    GYP_DEFINES="clang=1 target_arch=x64" ./gyp_libyuv
-    ninja -j7 -C out/Debug
-    ninja -j7 -C out/Release
+### macOS and Linux
 
-    GYP_DEFINES="clang=1 target_arch=ia32" ./gyp_libyuv
-    ninja -j7 -C out/Debug
-    ninja -j7 -C out/Release
+    gn gen out/Release "--args=is_debug=false"
+    gn gen out/Debug "--args=is_debug=true"
+    ninja -j7 -v -C out/Release
+    ninja -j7 -v -C out/Debug
+
+### Building Offical with GN
+
+    gn gen out/Official "--args=is_debug=false is_official_build=true is_chrome_branded=true"
+    ninja -C out/Official
 
 ### iOS
+This section needs an update to GN build documentation.
 http://www.chromium.org/developers/how-tos/build-instructions-ios
 
 Add to .gclient last line: `target_os=['ios'];`
 
 armv7
 
     GYP_DEFINES="OS=ios target_arch=armv7 target_subarch=arm32" GYP_CROSSCOMPILE=1 GYP_GENERATOR_FLAGS="output_dir=out_ios" ./gyp_libyuv
     ninja -j7 -C out_ios/Debug-iphoneos libyuv_unittest
     ninja -j7 -C out_ios/Release-iphoneos libyuv_unittest
 
@@ skipping 15 matching lines @@
     ninja -j7 -C out_sim/Debug-iphonesimulator libyuv_unittest
     ninja -j7 -C out_sim/Release-iphonesimulator libyuv_unittest
 
 ### Android
 https://code.google.com/p/chromium/wiki/AndroidBuildInstructions
 
 Add to .gclient last line: `target_os=['android'];`
 
 armv7
 
-    GYP_DEFINES="OS=android" GYP_CROSSCOMPILE=1 ./gyp_libyuv
-    ninja -j7 -C out/Debug yuv_unittest_apk
-    ninja -j7 -C out/Release yuv_unittest_apk
+    gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"arm\""
+    gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"arm\""
+    ninja -j7 -v -C out/Debug libyuv_unittest
+    ninja -j7 -v -C out/Release libyuv_unittest
 
 arm64
 
-    GYP_DEFINES="OS=android target_arch=arm64 target_subarch=arm64" GYP_CROSSCOMPILE=1 ./gyp_libyuv
-    ninja -j7 -C out/Debug yuv_unittest_apk
-    ninja -j7 -C out/Release yuv_unittest_apk
+    gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"arm64\""
+    gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"arm64\""
+    ninja -j7 -v -C out/Debug libyuv_unittest
+    ninja -j7 -v -C out/Release libyuv_unittest
 
 ia32
 
-    GYP_DEFINES="OS=android target_arch=ia32" GYP_CROSSCOMPILE=1 ./gyp_libyuv
-    ninja -j7 -C out/Debug yuv_unittest_apk
-    ninja -j7 -C out/Release yuv_unittest_apk
-
-    GYP_DEFINES="OS=android target_arch=ia32 android_full_debug=1" GYP_CROSSCOMPILE=1 ./gyp_libyuv
-    ninja -j7 -C out/Debug yuv_unittest_apk
+    gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"x86\""
+    gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"x86\""
+    ninja -j7 -v -C out/Debug libyuv_unittest
+    ninja -j7 -v -C out/Release libyuv_unittest
 
 mipsel
 
-    GYP_DEFINES="OS=android target_arch=mipsel" GYP_CROSSCOMPILE=1 ./gyp_libyuv
-    ninja -j7 -C out/Debug yuv_unittest_apk
-    ninja -j7 -C out/Release yuv_unittest_apk
+    gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"mipsel\" mips_arch_variant=\"r6\" mips_use_msa=true is_component_build=true is_clang=false"
+    gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"mipsel\"" mips_arch_variant=\"r6\" mips_use_msa=true is_component_build=true is_clang=false"
+    ninja -j7 -v -C out/Debug libyuv_unittest
+    ninja -j7 -v -C out/Release libyuv_unittest
 
-arm32 disassembly:
+    gn gen out/Release "--args=is_debug=false target_os=\"android\" target_cpu=\"mips64el\"" mips_arch_variant=\"r6\" mips_use_msa=true is_component_build=true is_clang=false"
+    gn gen out/Debug "--args=is_debug=true target_os=\"android\" target_cpu=\"mips64el\"" mips_arch_variant=\"r6\" mips_use_msa=true is_component_build=true is_clang=false"
+    ninja -j7 -v -C out/Debug libyuv_unittest
+    ninja -j7 -v -C out/Release libyuv_unittest
 
-    third_party/android_tools/ndk/toolchains/arm-linux-androideabi-4.9/prebuilt/linux-x86_64/bin/arm-linux-androideabi-objdump -d out/Release/obj/source/libyuv.row_neon.o
+arm disassembly:
 
-arm64 disassembly:
+    third_party/android_tools/ndk/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-objdump -d ./out/Release/obj/libyuv/row_common.o >row_common.txt
 
-    third_party/android_tools/ndk/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-objdump -d out/Release/obj/source/libyuv.row_neon64.o
+    third_party/android_tools/ndk/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-objdump -d ./out/Release/obj/libyuv_neon/row_neon.o >row_neon.txt
+
+    third_party/android_tools/ndk/toolchains/aarch64-linux-android-4.9/prebuilt/linux-x86_64/bin/aarch64-linux-android-objdump -d ./out/Release/obj/libyuv_neon/row_neon64.o >row_neon64.txt
 
 Running tests:
 
     util/android/test_runner.py gtest -s libyuv_unittest -t 7200 --verbose --release --gtest_filter=*
 
 Running test as benchmark:
 
-    util/android/test_runner.py gtest -s libyuv_unittest -t 7200 --verbose --release --gtest_filter=* -a "--libyuv_width=1280 --libyuv_height=720 --libyuv_repeat=999 --libyuv_flags=-1"
+    util/android/test_runner.py gtest -s libyuv_unittest -t 7200 --verbose --release --gtest_filter=* -a "--libyuv_width=1280 --libyuv_height=720 --libyuv_repeat=999 --libyuv_flags=-1  --libyuv_cpu_info=-1"
 
 Running test with C code:
 
     util/android/test_runner.py gtest -s libyuv_unittest -t 7200 --verbose --release --gtest_filter=* -a "--libyuv_width=1280 --libyuv_height=720 --libyuv_repeat=999 --libyuv_flags=1 --libyuv_cpu_info=1"
 
-#### Building with GN
-
-    gn gen out/Release "--args=is_debug=false target_cpu=\"x86\""
-    gn gen out/Debug "--args=is_debug=true target_cpu=\"x86\""
-    ninja -C out/Release
-    ninja -C out/Debug
-
-### Building Offical with GN
-
-    gn gen out/Official "--args=is_debug=false is_official_build=true is_chrome_branded=true"
-    ninja -C out/Official
-
-#### Building mips with GN
-
-mipsel
-    gn gen out/Default "--args=is_debug=false target_cpu=\"mipsel\" target_os = \"android\" mips_arch_variant = \"r6\" mips_use_msa = true is_component_build = true is_clang = false"
-    ninja -C out/Default
-
-mips64el
-    gn gen out/Default "--args=is_debug=false target_cpu=\"mips64el\" target_os = \"android\" mips_arch_variant = \"r6\" mips_use_msa = true is_component_build = true is_clang = false"
-    ninja -C out/Default
-
-### Linux
-
-    GYP_DEFINES="target_arch=x64" ./gyp_libyuv
-    ninja -j7 -C out/Debug
-    ninja -j7 -C out/Release
-
-    GYP_DEFINES="target_arch=ia32" ./gyp_libyuv
-    ninja -j7 -C out/Debug
-    ninja -j7 -C out/Release
-
-#### CentOS
-
-On CentOS 32 bit the following work around allows a sync:
-
-    export GYP_DEFINES="host_arch=ia32"
-    gclient sync
-
-### Windows Shared Library
-
-Modify libyuv.gyp from 'static_library' to 'shared_library', and add 'LIBYUV_BUILDING_SHARED_LIBRARY' to 'defines'.
-
-    gclient runhooks
-
-After this command follow the building the library instructions above.
-
-If you get a compile error for atlthunk.lib on Windows, read http://www.chromium.org/developers/how-tos/build-instructions-windows
-
-
 ### Build targets
 
     ninja -C out/Debug libyuv
     ninja -C out/Debug libyuv_unittest
     ninja -C out/Debug compare
     ninja -C out/Debug convert
     ninja -C out/Debug psnr
     ninja -C out/Debug cpuid
 
+### ARM Linux
+
+    gn gen out/Release "--args=is_debug=false target_cpu=\"arm64\""
+    gn gen out/Debug "--args=is_debug=true target_cpu=\"arm64\""
+    ninja -j7 -v -C out/Debug libyuv_unittest
+    ninja -j7 -v -C out/Release libyuv_unittest
 
 ## Building the Library with make
 
 ### Linux
 
     make -j7 V=1 -f linux.mk
     make -j7 V=1 -f linux.mk clean
     make -j7 V=1 -f linux.mk CXX=clang++
 
 ## Building the Library with cmake
 
 Install cmake: http://www.cmake.org/
 
 Default debug build:
 
     mkdir out
     cd out
     cmake ..
     cmake --build .
 
 Release build/install
 
     mkdir out
     cd out
     cmake -DCMAKE_INSTALL_PREFIX="/usr/lib" -DCMAKE_BUILD_TYPE="Release" ..
     cmake --build . --config Release
     sudo cmake --build . --target install --config Release
 
-### Windows 8 Phone
-
-Pre-requisite:
-
-* Install Visual Studio 2012 and Arm to your environment.<br>
-
-Then:
-
-    call "c:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\bin\x86_arm\vcvarsx86_arm.bat"
-
-or with Visual Studio 2013:
-
-    call "c:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\bin\x86_arm\vcvarsx86_arm.bat"
-    nmake /f winarm.mk clean
-    nmake /f winarm.mk
-
-### Windows Shared Library
-
-Modify libyuv.gyp from 'static_library' to 'shared_library', and add 'LIBYUV_BUILDING_SHARED_LIBRARY' to 'defines'. Then run this.
-
-    gclient runhooks
-
-After this command follow the building the library instructions above.
-
-If you get a compile error for atlthunk.lib on Windows, read http://www.chromium.org/developers/how-tos/build-instructions-windows
-
-### 64 bit Windows
-
-    set GYP_DEFINES=target_arch=x64
-    gclient runhooks V=1
-
-### ARM Linux
-
-    export GYP_DEFINES="target_arch=arm"
-    export CROSSTOOL=`<path>`/arm-none-linux-gnueabi
-    export CXX=$CROSSTOOL-g++
-    export CC=$CROSSTOOL-gcc
-    export AR=$CROSSTOOL-ar
-    export AS=$CROSSTOOL-as
-    export RANLIB=$CROSSTOOL-ranlib
-    gclient runhooks
-
 ## Running Unittests
 
 ### Windows
 
     out\Release\libyuv_unittest.exe --gtest_catch_exceptions=0 --gtest_filter="*"
 
 ### OSX
 
     out/Release/libyuv_unittest --gtest_filter="*"
 
 ### Linux
 
     out/Release/libyuv_unittest --gtest_filter="*"
 
 Replace --gtest_filter="*" with specific unittest to run.  May include wildcards. e.g.
 
-    out/Release/libyuv_unittest --gtest_filter=libyuvTest.I420ToARGB_Opt
+    out/Release/libyuv_unittest --gtest_filter=*I420ToARGB_Opt
 
 ## CPU Emulator tools
 
 ### Intel SDE (Software Development Emulator)
 
-Pre-requisite: Install IntelSDE for Windows: http://software.intel.com/en-us/articles/intel-software-development-emulator
+Pre-requisite: Install IntelSDE: http://software.intel.com/en-us/articles/intel-software-development-emulator
 
 Then run:
 
-    c:\intelsde\sde -hsw -- out\release\libyuv_unittest.exe --gtest_filter=*
+    c:\intelsde\sde -hsw -- out\Release\libyuv_unittest.exe --gtest_filter=*
 
+    ~/intelsde/sde -skx -- out/Release/libyuv_unittest --gtest_filter=**I420ToARGB_Opt
 
-## Memory tools
+## Sanitizers
+
+    gn gen out/Debug "--args=is_debug=true is_asan=true"
+    ninja -j7 -v -C out/Debug
+
+    Sanitizers available: tsan, msan, asan, ubsan, lsan
 
 ### Running Dr Memory memcheck for Windows
 
 Pre-requisite: Install Dr Memory for Windows and add it to your path: http://www.drmemory.org/docs/page_install_windows.html
 
-    set GYP_DEFINES=build_for_tool=drmemory target_arch=ia32
-    call python gyp_libyuv -fninja -G msvs_version=2013
-    ninja -C out\Debug
     drmemory out\Debug\libyuv_unittest.exe --gtest_catch_exceptions=0 --gtest_filter=*
-
-### Running UBSan
-
-See Chromium instructions for sanitizers: https://www.chromium.org/developers/testing/undefinedbehaviorsanitizer
-
-Sanitizers available: TSan, MSan, ASan, UBSan, LSan
-
-    GYP_DEFINES='ubsan=1' gclient runhooks
-    ninja -C out/Release
-
-### Running Valgrind memcheck
-
-Memory errors and race conditions can be found by running tests under special memory tools. [Valgrind] [1] is an instrumentation framework for building dynamic analysis tools. Various tests and profilers are built upon it to find memory handling errors and memory leaks, for instance.
-
-[1]: http://valgrind.org
-
-    solutions = [
-      { "name"        : "libyuv",
-        "url"         : "https://chromium.googlesource.com/libyuv/libyuv",
-        "deps_file"   : "DEPS",
-        "managed"     : True,
-        "custom_deps" : {
-           "libyuv/chromium/src/third_party/valgrind": "https://chromium.googlesource.com/chromium/deps/valgrind/binaries",
-        },
-        "safesync_url": "",
-      },
-    ]
-
-Then run:
-
-    GYP_DEFINES="clang=0 target_arch=x64 build_for_tool=memcheck" python gyp_libyuv
-    ninja -C out/Debug
-    valgrind out/Debug/libyuv_unittest
-
-
-For more information, see http://www.chromium.org/developers/how-tos/using-valgrind
-
-### Running Thread Sanitizer (TSan)
-
-    GYP_DEFINES="clang=0 target_arch=x64 build_for_tool=tsan" python gyp_libyuv
-    ninja -C out/Debug
-    valgrind out/Debug/libyuv_unittest
-
-For more info, see http://www.chromium.org/developers/how-tos/using-valgrind/threadsanitizer
-
-### Running Address Sanitizer (ASan)
-
-    GYP_DEFINES="clang=0 target_arch=x64 build_for_tool=asan" python gyp_libyuv
-    ninja -C out/Debug
-    valgrind out/Debug/libyuv_unittest
-
-For more info, see http://dev.chromium.org/developers/testing/addresssanitizer
-
-## Benchmarking
-
-The unittests can be used to benchmark.
-
-### Windows
-
-    set LIBYUV_WIDTH=1280
-    set LIBYUV_HEIGHT=720
-    set LIBYUV_REPEAT=999
-    set LIBYUV_FLAGS=-1
-    out\Release\libyuv_unittest.exe --gtest_filter=*I420ToARGB_Opt
-
-
-### Linux and Mac
-
-    LIBYUV_WIDTH=1280 LIBYUV_HEIGHT=720 LIBYUV_REPEAT=1000 out/Release/libyuv_unittest --gtest_filter=*I420ToARGB_Opt
-
-    libyuvTest.I420ToARGB_Opt (547 ms)
-
-Indicates 0.547 ms/frame for 1280 x 720.
-
-## Making a change
-
-    gclient sync
-    git checkout -b mycl -t origin/master
-    git pull
-    <edit files>
-    git add -u
-    git commit -m "my change"
-    git cl lint
-    git cl try
-    git cl upload -r a-reviewer@chomium.org -s
-    <once approved..>
-    git cl land