stagefright: add AString constructor from String8

Change-Id: I85b37b6dee4ea9d5f7f1c1a40ff405a01a0c67f1
diff --git a/include/media/stagefright/foundation/AString.h b/include/media/stagefright/foundation/AString.h
index 0f8f1e1..622028e 100644
--- a/include/media/stagefright/foundation/AString.h
+++ b/include/media/stagefright/foundation/AString.h
@@ -22,10 +22,13 @@
 
 namespace android {
 
+struct String8;
+
 struct AString {
     AString();
     AString(const char *s);
     AString(const char *s, size_t size);
+    AString(const String8 &from);
     AString(const AString &from);
     AString(const AString &from, size_t offset, size_t n);
     ~AString();
diff --git a/media/libstagefright/foundation/AString.cpp b/media/libstagefright/foundation/AString.cpp
index dee786d..fcd825f 100644
--- a/media/libstagefright/foundation/AString.cpp
+++ b/media/libstagefright/foundation/AString.cpp
@@ -20,6 +20,7 @@
 #include <stdlib.h>
 #include <string.h>
 
+#include <utils/String8.h>
 #include "ADebug.h"
 #include "AString.h"
 
@@ -48,6 +49,13 @@
     setTo(s, size);
 }
 
+AString::AString(const String8 &from)
+    : mData(NULL),
+      mSize(0),
+      mAllocSize(1) {
+    setTo(from.string(), from.length());
+}
+
 AString::AString(const AString &from)
     : mData(NULL),
       mSize(0),