Add SkData::NewFromFD.

src/core/SkData.cpp

Index: src/core/SkData.cpp
===================================================================
--- src/core/SkData.cpp	(revision 9384)
+++ src/core/SkData.cpp	(working copy)
@@ -97,6 +97,16 @@
     return SkData::NewWithProc(addr, size, sk_mmap_releaseproc, NULL);
 }
 
+SkData* SkData::NewFromFD(int fd) {
+    size_t size;
+    void* addr = sk_fdmmap(fd, &size);
+    if (NULL == addr) {
+        return NULL;
+    }
+
+    return SkData::NewWithProc(addr, size, sk_mmap_releaseproc, NULL);
+}
+
 // assumes context is a SkData
 static void sk_dataref_releaseproc(const void*, size_t, void* context) {
     SkData* src = reinterpret_cast<SkData*>(context);