Use a valid /prefetch argument when launching a process.

components/nacl.gyp

Index: components/nacl.gyp
diff --git a/components/nacl.gyp b/components/nacl.gyp
index a9ed69cd269fb349c96367d86c07ded032aae1bc..2fd7aba4613ee3b061aa5d5f482ab9e4ca2a747c 100644
--- a/components/nacl.gyp
+++ b/components/nacl.gyp
@@ -139,6 +139,13 @@
                 '../sandbox/sandbox.gyp:sandbox_services',
               ]
             }],
+            ['OS=="win"', {
+              'dependencies': [
+                # TODO(fdoray): Remove this once the PreRead field trial has
+                # expired. crbug.com/577698
+                '../components/components.gyp:startup_metric_utils_common',
+              ]
+            }],
           ],
         },
         {