Merge tcmalloc r111 (perftools v. 1.8) with the chromium/ branch.

third_party/tcmalloc/chromium/src/base/cycleclock.h

Index: third_party/tcmalloc/chromium/src/base/cycleclock.h
===================================================================
--- third_party/tcmalloc/chromium/src/base/cycleclock.h	(revision 94429)
+++ third_party/tcmalloc/chromium/src/base/cycleclock.h	(working copy)
@@ -50,16 +50,18 @@
 #if defined(__MACH__) && defined(__APPLE__)
 # include <mach/mach_time.h>
 #endif
-// For MSVC, we want the __rdtsc intrinsic, declared in <intrin.h>.
-// Unfortunately, in some environments, <windows.h> and <intrin.h> have
-// conflicting declarations of some other intrinsics, breaking compilation.
+// For MSVC, we want to use '_asm rdtsc' when possible (since it works
+// with even ancient MSVC compilers), and when not possible the
+// __rdtsc intrinsic, declared in <intrin.h>.  Unfortunately, in some
+// environments, <windows.h> and <intrin.h> have conflicting
+// declarations of some other intrinsics, breaking compilation.
 // Therefore, we simply declare __rdtsc ourselves. See also
 // http://connect.microsoft.com/VisualStudio/feedback/details/262047
-#if defined(_MSC_VER)
+#if defined(_MSC_VER) && !defined(_M_IX86)
 extern "C" uint64 __rdtsc();
 #pragma intrinsic(__rdtsc)
 #endif
-#ifdef HAVE_SYS_TIME_H
+#ifdef ARMV3
 #include <sys/time.h>
 #endif
 
@@ -108,6 +110,12 @@
     int64 itc;
     asm("mov %0 = ar.itc" : "=r" (itc));
     return itc;
+#elif defined(_MSC_VER) && defined(_M_IX86)
+    // Older MSVC compilers (like 7.x) don't seem to support the
+    // __rdtsc intrinsic properly, so I prefer to use _asm instead
+    // when I know it will work.  Otherwise, I'll use __rdtsc and hope
+    // the code is being compiled with a non-ancient compiler.
+    _asm rdtsc
 #elif defined(_MSC_VER)
     return __rdtsc();
 #elif defined(ARMV3)