Add mspdbcmf (un-fastlink) support to StripChromeSymbols.py

When binaries are built with /debug:fastlink they are smaller and
require less copying of data, but they cannot be stripped by
pdbcopy.exe. This means that StripChromeSymbols.py fails with locally
built binaries if /debug:fastlink is used, which gets us back to
WPA taking ~25 minutes to process Chrome's symbols.

This change automatically runs mspdbcmf.exe (if present) if pdbcopy
fails. Hacks upon hacks upon hacks. All of this could be avoided if
WPA could load Chrome's symbols quickly. Someday...

This fixes issue #77

Author: randomascii

bin/StripChromeSymbols.py

@@ -70,6 +70,13 @@ def main():
     if os.path.exists(pdbcopy_install):
       pdbcopy_path = pdbcopy_install
 
+  # This tool converts PDBs created with /debug:fastlink (VC++ 2015 feature) to
+  # regular PDBs that contain all of the symbol information directly. This is
+  # required so that pdbcopy can copy the symbols.
+  un_fastlink_tool = r"C:\Program Files (x86)\Microsoft Visual Studio 14.0\VC\bin\amd64\mspdbcmf.exe"
+  if not os.path.exists(un_fastlink_tool):
+    un_fastlink_tool = None
+
   # RetrieveSymbols.exe requires some support files. dbghelp.dll and symsrv.dll
   # have to be in the same directory as RetrieveSymbols.exe and pdbcopy.exe must
   # be in the path, so copy them all to the script directory.
@@ -167,9 +174,25 @@ def main():
           # it to fail. So don't do that.
           copy_command = '%s "%s" "%s" -p' % (pdbcopy_path, pdb_cache_path, dest_path)
           print("  > %s" % copy_command)
-          output = str(subprocess.check_output(copy_command, stderr=subprocess.STDOUT))
-          if output:
-            print("  %s" % output, end="")
+          if un_fastlink_tool:
+            # If the un_fastlink_tool is available then run the pdbcopy command in a
+            # try block. If pdbcopy fails then run the un_fastlink_tool and try again.
+            try:
+              output = str(subprocess.check_output(copy_command, stderr=subprocess.STDOUT))
+              if output:
+                print("  %s" % output, end="")
+            except:
+              convert_command = '%s "%s"' % (un_fastlink_tool, pdb_cache_path)
+              print("Attempting to un-fastlink PDB so that pdbcopy can strip it. This may be slow.")
+              print("  > %s" % convert_command)
+              subprocess.check_output(convert_command)
+              output = str(subprocess.check_output(copy_command, stderr=subprocess.STDOUT))
+              if output:
+                print("  %s" % output, end="")
+          else:
+            output = str(subprocess.check_output(copy_command, stderr=subprocess.STDOUT))
+            if output:
+              print("  %s" % output, end="")
           if not os.path.exists(dest_path):
             print("Aborting symbol generation because stripped PDB '%s' does not exist. WPA symbol loading may be slow." % dest_path)
             sys.exit(0)