Fix bisect-builds.py crash for non-official win64 builds

tools/bisect-builds.py

Index: tools/bisect-builds.py
diff --git a/tools/bisect-builds.py b/tools/bisect-builds.py
index e89ce104242a68fdc825c92ceac1b0e33838fcf1..038ecea1b30057ade64225eae2400869989f0389 100755
--- a/tools/bisect-builds.py
+++ b/tools/bisect-builds.py
@@ -155,8 +155,11 @@ class PathContext(object):
     elif self.platform in ('mac', 'mac64'):
       self._listing_platform_dir = 'Mac/'
       self._binary_name = 'Chromium.app/Contents/MacOS/Chromium'
-    elif self.platform == 'win':
-      self._listing_platform_dir = 'Win/'
+    elif self.platform in ('win', 'win64'):

[Jamie Madill, 2016/09/22 13:55:22]

since these only use self._listing_platform_dir, I would probably flatten the
nested ifs to the elif level.

+      if self.platform == 'win':
+        self._listing_platform_dir = 'Win/'
+      elif self.platform == 'win64':
+        self._listing_platform_dir = 'Win_x64/'
 
   def GetASANPlatformDir(self):
     """ASAN builds are in directories like "linux-release", or have filenames