Allow sanitizer coverage to create *.sancov files when sandboxed

content/common/sandbox_win.cc

Index: content/common/sandbox_win.cc
diff --git a/content/common/sandbox_win.cc b/content/common/sandbox_win.cc
index 915f145d0ff74500ab39c449e54f558985beb652..08f5dd91eb962afce5e995ae7bc5d81ad2921245 100644
--- a/content/common/sandbox_win.cc
+++ b/content/common/sandbox_win.cc
@@ -359,6 +359,26 @@ bool AddGenericPolicy(sandbox::TargetPolicy* policy) {
     return false;
 #endif
 
+#if defined(SANITIZER_COVERAGE)
+  DWORD coverage_dir_size =
+      ::GetEnvironmentVariable(L"SANITIZER_COVERAGE_DIR", NULL, 0);
+  if (coverage_dir_size == 0) {
+    LOG(WARNING) << "SANITIZER_COVERAGE_DIR was not set, coverage won't work.";
+  } else {
+    std::wstring coverage_dir(coverage_dir_size);
+    coverage_dir_size = ::GetEnvironmentVariable(
+        L"SANITIZER_COVERAGE_DIR", coverage_dir.data(), coverage_dir_size);

[cpu_(ooo_6.6-7.5), 2015/05/12 00:53:56]

lgtm, please use base's  WriteInto() instead of 368 + 376 and for the record
trying to fend off SANITIZER_COVERAGE_DIR size change between the two calls is
not worth it, but if you really really want it you can have it.

[Reid Kleckner, 2015/05/12 16:03:07]

Sure. I felt like the CHECK was calling out the assumption that nobody is racing
in and changing this env var while Chrome is running.

+    CHECK(coverage_dir.size() == coverage_dir_size);
+    base::FilePath sancov_path =
+        base::FilePath(coverage_dir).Append(L"*.sancov");
+    result = policy->AddRule(sandbox::TargetPolicy::SUBSYS_FILES,
+                             sandbox::TargetPolicy::FILES_ALLOW_ANY,
+                             sancov_path.value().c_str());
+    if (result != sandbox::SBOX_ALL_OK)
+      return false;
+  }
+#endif
+
   AddGenericDllEvictionPolicy(policy);
   return true;
 }