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/app/doc.go

-// Copyright 2014 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-/*
-Package app lets you write Apps for Android (and eventually, iOS).
-
-There are two ways to use Go in an Android App. The first is as a
-library called from Java, the second is to use a restricted set of
-features but work entirely in Go.
-
-Shared Library
-
-A Go program can be compiled for Android as a shared library. JNI
-methods can be implemented via cgo, or generated automatically with
-gobind: http://golang.org/x/mobile/cmd/gobind
-
-The library must include a package main and a main function that does
-not return until the process exits. Libraries can be cross-compiled
-using the Android NDK and the Go tool:
-
-        GOOS=android GOARCH=arm GOARM=7 CGO_ENABLED=1 \
-        go build -ldflags="-shared" .
-
-See http://golang.org/x/mobile/example/libhello for an example of
-calling into a Go shared library from a Java Android app.
-
-Native App
-
-An app can be written entirely in Go. This results in a significantly
-simpler programming environment (and eventually, portability to iOS),
-however only a very restricted set of Android APIs are available.
-
-The provided interfaces are focused on games. It is expected that the
-app will draw to the entire screen (via OpenGL, see the go.mobile/gl
-package), and that none of the platform's screen management
-infrastructure is exposed. On Android, this means a native app is
-equivalent to a single Activity (in particular a NativeActivity) and
-on iOS, a single UIWindow. Touch events will be accessible via this
-package. When Android support is out of preview, all APIs supported by
-the Android NDK will be exposed via a Go package.
-
-See http://golang.org/x/mobile/example/sprite for an example app.
-
-Lifecycle in Native Apps
-
-App execution begins in platform-specific code. Early on in the app's
-life, the Go runtime is initialized and the Go main function is called.
-(For Android, this is in ANativeActivity_onCreate, for iOS,
-application:willFinishLaunchingWithOptions.)
-
-An app is expected to call the Run function in its main. When the main
-function exits, the app exits.
-
-        package main
-
-        import (
-                "log"
-
-                "golang.org/x/mobile/app"
-        )
-
-        func main() {
-                app.Run(app.Callbacks{
-                        Draw: draw,
-                })
-        }
-
-        func draw() {
-                log.Print("In draw loop, can call OpenGL.")
-        }
-
-*/
-package app // import "golang.org/x/mobile/app"