Remove third_party/golang.org/x/mobile as it is no longer used with Go 1.5.

third_party/go/src/golang.org/x/mobile/Dockerfile

-# Dockerfile to build an image with the local version of golang.org/x/mobile.
-#
-#  > docker build -t mobile $GOPATH/src/golang.org/x/mobile
-#  > docker run -it --rm -v $GOPATH/src:/src mobile
-
-FROM ubuntu:12.04
-
-# Install system-level dependencies.
-ENV DEBIAN_FRONTEND noninteractive
-RUN echo "debconf shared/accepted-oracle-license-v1-1 select true" | debconf-set-selections && \
-        echo "debconf shared/accepted-oracle-license-v1-1 seen true" | debconf-set-selections
-RUN apt-get update && \
-        apt-get -y install build-essential python-software-properties bzip2 unzip curl \
-                git subversion mercurial bzr \
-                libncurses5:i386 libstdc++6:i386 zlib1g:i386 && \
-        add-apt-repository ppa:webupd8team/java && \
-        apt-get update && \
-        apt-get -y install oracle-java6-installer
-
-# Install Ant.
-RUN curl -L http://archive.apache.org/dist/ant/binaries/apache-ant-1.9.2-bin.tar.gz | tar xz -C /usr/local
-ENV ANT_HOME /usr/local/apache-ant-1.9.2
-
-# Install Android SDK.
-RUN curl -L http://dl.google.com/android/android-sdk_r23.0.2-linux.tgz | tar xz -C /usr/local
-ENV ANDROID_HOME /usr/local/android-sdk-linux
-RUN echo y | $ANDROID_HOME/tools/android update sdk --no-ui --all --filter build-tools-19.1.0 && \
-        echo y | $ANDROID_HOME/tools/android update sdk --no-ui --all --filter platform-tools && \
-        echo y | $ANDROID_HOME/tools/android update sdk --no-ui --all --filter android-19
-
-# Install Android NDK.
-RUN curl -L http://dl.google.com/android/ndk/android-ndk-r9d-linux-x86_64.tar.bz2 | tar xj -C /usr/local
-ENV NDK_ROOT /usr/local/android-ndk-r9d
-RUN $NDK_ROOT/build/tools/make-standalone-toolchain.sh --platform=android-9 --install-dir=$NDK_ROOT --system=linux-x86_64
-
-# Install Gradle 2.1
-# : android-gradle compatibility
-#   http://tools.android.com/tech-docs/new-build-system/version-compatibility
-RUN curl -L http://services.gradle.org/distributions/gradle-2.1-all.zip -o /tmp/gradle-2.1-all.zip && unzip /tmp/gradle-2.1-all.zip -d /usr/local && rm /tmp/gradle-2.1-all.zip
-ENV GRADLE_HOME /usr/local/gradle-2.1
-
-# Update PATH for the above.
-ENV PATH $PATH:$ANDROID_HOME/tools
-ENV PATH $PATH:$ANDROID_HOME/platform-tools
-ENV PATH $PATH:$NDK_ROOT
-ENV PATH $PATH:$ANT_HOME/bin
-ENV PATH $PATH:$GRADLE_HOME/bin
-
-# Install Go.
-#   1) 1.4 for bootstrap.
-ENV GOROOT_BOOTSTRAP /go1.4
-RUN (curl -sSL https://golang.org/dl/go1.4.linux-amd64.tar.gz | tar -vxz -C /tmp) && \
-        mv /tmp/go $GOROOT_BOOTSTRAP
-
-
-#   2) Download and cross compile the Go on revision GOREV.
-#
-# GOVERSION string is the output of 'git log -n 1 --format="format: devel +%h %cd" HEAD'
-# like in go tool dist.
-# Revision picked on Jan 21, 2015.
-ENV GO_REV      34bc85f6f3b02ebcd490b40f4d32907ff2e69af3
-ENV GO_VERSION  devel +34bc85f Wed Jan 21 21:30:46 2015 +0000
-
-ENV GOROOT /go
-ENV GOPATH /
-ENV PATH $PATH:$GOROOT/bin
-
-RUN mkdir -p $GOROOT && \
-        curl -sSL "https://go.googlesource.com/go/+archive/$GO_REV.tar.gz" | tar -vxz -C $GOROOT && \
-        echo $GO_VERSION > $GOROOT/VERSION && \
-        cd $GOROOT/src && \
-        ./all.bash && \
-        CC_FOR_TARGET=$NDK_ROOT/bin/arm-linux-androideabi-gcc GOOS=android GOARCH=arm GOARM=7 ./make.bash
-
-# Expect the GOPATH/src volume to be mounted.  (-v $GOPATH/src:/src)
-VOLUME ["/src"]
-
-# Generate a debug keystore to avoid it being generated on each `docker run`
-# and fail `adb install -r <apk>` with a conflicting certificate error.
-RUN keytool -genkeypair -alias androiddebugkey -keypass android -keystore ~/.android/debug.keystore -storepass android -dname "CN=Android Debug,O=Android,C=US" -validity 365
-
-WORKDIR $GOPATH/src/golang.org/x/mobile