Only add pdb to isolate when fastbuild!=2.

BUG=414808
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Review URL: https://codereview.chromium.org/589633002

Cr-Commit-Position: refs/heads/master@{#295754}
diff --git a/content/content_unittests.isolate b/content/content_unittests.isolate
index 1303b98f..e689a671 100644
--- a/content/content_unittests.isolate
+++ b/content/content_unittests.isolate
@@ -76,6 +76,10 @@
           '<(PRODUCT_DIR)/ffmpegsumo.dll',
           '<(PRODUCT_DIR)/osmesa.dll',
         ],
+      },
+    }],
+    ['OS=="win" and (fastbuild==0 or fastbuild==1)', {
+      'variables': {
         'isolate_dependency_untracked': [
           '<(PRODUCT_DIR)/content_unittests.exe.pdb',
         ],