Return true when file size is zero.

base/test/test_file_util_mac.cc

Index: base/test/test_file_util_mac.cc
diff --git a/base/test/test_file_util_mac.cc b/base/test/test_file_util_mac.cc
index 316b5c3d01aa9aec7c42d64bce64be95cd0b0969..ea299a63e6f5f7d79ca0f0f669a9f0993166a1f5 100644
--- a/base/test/test_file_util_mac.cc
+++ b/base/test/test_file_util_mac.cc
@@ -17,15 +17,28 @@ bool EvictFileFromSystemCache(const FilePath& file) {
   // default) + MAP_SHARED, then do an msync to invalidate the memory.  The next
   // open should then have to load the file from disk.
 
+  int64 length;
+  if (!file_util::GetFileSize(file, &length)) {
+    LOG(ERROR) << "failed to get size of " << file.value();
+    return false;
+  }
+
+  // When a file is empty, we do not need to evict it from cache.
+  // In fact, an attempt to map it to memory will result in error.
+  if (length == 0) {
+    LOG(WARNING) << "file size is zero, will not attempt to map to memory";
+    return true;
+  }
+
   file_util::MemoryMappedFile mapped_file;
   if (!mapped_file.Initialize(file)) {
-    DLOG(WARNING) << "failed to memory map " << file.value();
+    LOG(WARNING) << "failed to memory map " << file.value();
     return false;
   }
 
   if (msync(const_cast<uint8*>(mapped_file.data()), mapped_file.length(),
             MS_INVALIDATE) != 0) {
-    DLOG(WARNING) << "failed to invalidate memory map of " << file.value()
+    LOG(WARNING) << "failed to invalidate memory map of " << file.value()
         << ", errno: " << errno;
     return false;
   }