Fail if an isolate entry refers to a missing file.

chrome/chrome.isolate

Index: chrome/chrome.isolate
diff --git a/chrome/chrome.isolate b/chrome/chrome.isolate
index d85689d0f7da875d170c2bcbf37306ddb127c617..c59555ff7838487bc0f4e0553eb84669840ba9e9 100644
--- a/chrome/chrome.isolate
+++ b/chrome/chrome.isolate
@@ -61,11 +61,17 @@
           '<(PRODUCT_DIR)/chrome_elf.dll',
           '<(PRODUCT_DIR)/ffmpegsumo.dll',
           '<(PRODUCT_DIR)/libexif.dll',
-          '<(PRODUCT_DIR)/nacl64<(EXECUTABLE_SUFFIX)',
           '<(PRODUCT_DIR)/osmesa.dll',
         ],
       },
     }],
+    ['OS=="win" and target_arch=="ia32"', {
+      'variables': {
+        'isolate_dependency_tracked': [
+          '<(PRODUCT_DIR)/nacl64.exe',

[M-A Ruel, 2014/09/18 15:38:52]

You mean 32?

[jam, 2014/09/18 15:44:44]

nacl64.exe is needed with 32 bit builds of Chrome when they're run on a 64 bit
version of Windows. For 64-bit versions of Chrome, no such binary is needed

+        ],
+      },
+    }],
     ['OS=="win" and component=="static_library"', {
       'variables': {
         'isolate_dependency_tracked': [