move SK_MMAP_SUPPORT into SkPreConfig, so we can know about its availability

trunk/src/core/SkData.cpp

Index: trunk/src/core/SkData.cpp
===================================================================
--- trunk/src/core/SkData.cpp	(revision 8197)
+++ trunk/src/core/SkData.cpp	(working copy)
@@ -8,6 +8,13 @@
 #include "SkData.h"
 #include "SkFlattenableBuffers.h"
 
+#if SK_MMAP_SUPPORT
+    #include <unistd.h>
+    #include <sys/mman.h>
+    #include <fcntl.h>
+    #include <errno.h>
+#endif
+
 SK_DEFINE_INST_COUNT(SkData)
 
 SkData::SkData(const void* ptr, size_t size, ReleaseProc proc, void* context) {
@@ -120,6 +127,20 @@
     return NewWithCopy(cstr, size);
 }
 
+#if SK_MMAP_SUPPORT
+static void sk_munmap_releaseproc(const void* addr, size_t length, void*) {
+    munmap(const_cast<void*>(addr), length);
+}
+
+SkData* SkData::NewFromMMap(const void* addr, size_t length) {
+    return SkNEW_ARGS(SkData, (addr, length, sk_munmap_releaseproc, NULL));
+}
+#else
+SkData* SkData::NewFromMMap(const void* addr, size_t length) {
+    return NULL;
+}
+#endif
+
 ///////////////////////////////////////////////////////////////////////////////
 
 void SkData::flatten(SkFlattenableWriteBuffer& buffer) const {
@@ -300,3 +321,4 @@
     gEmptySet->ref();
     return gEmptySet;
 }
+