Fixed all unused-variable Clang warnings on Windows.

components/crash/app/breakpad_win.cc

Index: components/crash/app/breakpad_win.cc
diff --git a/components/crash/app/breakpad_win.cc b/components/crash/app/breakpad_win.cc
index bfce051a60e2c2951891b93a6971f7d01190c419..bee4fab757feb8c6df1bb999d38a92187fe72c8b 100644
--- a/components/crash/app/breakpad_win.cc
+++ b/components/crash/app/breakpad_win.cc
@@ -94,9 +94,11 @@ const wchar_t kSystemPrincipalSid[] =L"S-1-5-18";
 google_breakpad::ExceptionHandler* g_breakpad = NULL;
 google_breakpad::ExceptionHandler* g_dumphandler_no_crash = NULL;
 
+#if !defined(_WIN64)
 EXCEPTION_POINTERS g_surrogate_exception_pointers = {0};
 EXCEPTION_RECORD g_surrogate_exception_record = {0};
 CONTEXT g_surrogate_context = {0};
+#endif  // !defined(_WIN64)
 
 typedef NTSTATUS (WINAPI* NtTerminateProcessPtr)(HANDLE ProcessHandle,
                                                  NTSTATUS ExitStatus);