MemorySanitizer: improve the udev dynamic loading hack.

Use the unversioned symlink to ensure we always load instrumented udev.

BUG=437464, 438427
R=thestig@chromium.org, reillyg@chromium.org

Review URL: https://codereview.chromium.org/755873003

Cr-Commit-Position: refs/heads/master@{#307067}

device/udev_linux/udev0_loader.cc

@@ -18,7 +18,14 @@ bool Udev0Loader::Init() {
   if (lib_loader_)
     return lib_loader_->loaded();
   lib_loader_.reset(new LibUdev0Loader);
+#if defined(MEMORY_SANITIZER)
+  // Temporary hack: rely on the symlink to pick up whichever *instrumented*
+  // version of libudev we have, be it libudev0 or libudev1. crbug.com/437464
+  // TODO(earthdok): Remove this hack after upgrading our LKGR builders.
+  return lib_loader_->Load("libudev.so");
+#else
   return lib_loader_->Load("libudev.so.0");
+#endif
 }
 
 const char* Udev0Loader::udev_device_get_action(udev_device* udev_device) {

device/udev_linux/udev_loader.cc

@@ -26,7 +26,7 @@ UdevLoader* UdevLoader::Get() {
   // will only build an instrumented copy of libudev0 and not libudev1. If one
   // runs the binary on Trusty, it will end up loading an uninstrumented
   // libudev1 at run time. http://crbug.com/437464
-  // TODO(thestig): Remove this after upgrading our MSAN LKGR builders to
+  // TODO(earthdok): Remove this after upgrading our MSAN LKGR builders to
   // Trusty.
 #if !defined(MEMORY_SANITIZER)
   udev_loader.reset(new Udev1Loader);