internal/mobileinit: new package for shared logic

Package app contains some logic that we want to share with
gobind-based libraries. So move it to a new internal package
that both can import.

Long term the log changes should be in the standard library,
but the Go tree is currently frozen.

Fixes golang/go#11630.

Change-Id: I9ff622fc499bf255bce18df23cb68b03f667947f
Reviewed-on: https://go-review.googlesource.com/11981
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>

app/app.go

@@ -6,7 +6,10 @@
 
 package app
 
-import "golang.org/x/mobile/event"
+import (
+	"golang.org/x/mobile/event"
+	_ "golang.org/x/mobile/internal/mobileinit"
+)
 
 // Main is called by the main.main function to run the mobile application.
 //

bind/seq/seq.go

@@ -16,7 +16,11 @@ package seq // import "golang.org/x/mobile/bind/seq"
 //	bindings which requires deconstructing seq into something
 //	gnarly. So don't get too attached to the design.
 
-import "fmt"
+import (
+	"fmt"
+
+	_ "golang.org/x/mobile/internal/mobileinit"
+)
 
 // Transact calls a method on a foreign object instance.
 // It blocks until the call is complete.

internal/mobileinit/mobileinit.go

@@ -0,0 +1,9 @@
+// Copyright 2015 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 mobileinit contains common initialization logic for mobile platforms
+// that is relevant to both all-Go apps and gobind-based apps.
+//
+// Long-term, any code in this package should consider moving into Go stdlib.
+package mobileinit

internal/mobileinit/mobileinit_android.go

@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-package app
+package mobileinit
 
 /*
 To view the log output run:
@@ -16,6 +16,8 @@ adb logcat GoLog:I *:S
 // Unfortunately, logcat is line oriented, so we must buffer.
 
 /*
+#cgo LDFLAGS: -landroid -llog
+
 #include <android/log.h>
 #include <string.h>
 */
@@ -37,7 +39,7 @@ type infoWriter struct{}
 
 func (infoWriter) Write(p []byte) (n int, err error) {
 	cstr := C.CString(string(p))
-	C.__android_log_write(C.ANDROID_LOG_INFO, ctagLog, cstr)
+	C.__android_log_write(C.ANDROID_LOG_INFO, ctag, cstr)
 	C.free(unsafe.Pointer(cstr))
 	return len(p), nil
 }