Enable --nacl-gdb flag on Linux.

chrome/browser/nacl_host/test/mock_nacl_gdb.cc

Index: chrome/browser/nacl_host/test/mock_nacl_gdb.cc
===================================================================
--- chrome/browser/nacl_host/test/mock_nacl_gdb.cc	(revision 130109)
+++ chrome/browser/nacl_host/test/mock_nacl_gdb.cc	(working copy)
@@ -9,13 +9,24 @@
 #include "base/environment.h"
 #include "base/file_util.h"
 #include "base/logging.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/process_util.h"
 
 static const char kArgs[] = "--args";
 static const char kEvalCommand[] = "--eval-command";
 static const char kNaClIrt[] = "nacl-irt ";
 static const char kPass[] = "PASS";
+static const char kDump[] = "dump binary value ";
+static const char kAttach[] = "attach ";
 
+// Send message to child nacl_helper
+void SendMessage(const char* arg) {
+  const char* file_end = strchr(arg, ' ');
+  CHECK(file_end);
+  char buf = '\0';
+  file_util::WriteFile(FilePath(FilePath::StringType(arg, file_end)), &buf, 1);
+}
+
 int main(int argc, char** argv) {
   scoped_ptr<base::Environment> env(base::Environment::Create());
   std::string mock_nacl_gdb_file;
@@ -34,6 +45,8 @@
   PCHECK(irt_file);
   fclose(irt_file);
   int i = 3;
+  bool has_attach_cmd = false;
+  char* message_pipe = NULL;
   // Skip additional --eval-command parameters.
   while (i < argc) {
     if (strcmp(argv[i], kArgs) == 0) {
@@ -44,11 +57,23 @@
       i += 2;
       // Command line shouldn't end with --eval-command switch without value.
       CHECK_LE(i, argc);
+      if (strncmp(argv[i - 1], kDump, sizeof(kDump) - 1) == 0) {
+        message_pipe = argv[i - 1] + sizeof(kDump) - 1;
+      } else if (strncmp(argv[i - 1], kAttach, sizeof(kAttach) - 1) == 0) {
+        has_attach_cmd = true;
+      }
       continue;
     }
     // Unknown argument.
     NOTREACHED() << "Invalid argument " << argv[i];
   }
+  if (has_attach_cmd) {
+    CHECK_EQ(i, argc);
+    CHECK(message_pipe);
+    // Test passed, so we can let NaCl launching to continue.
+    SendMessage(message_pipe);
+    return 0;
+  }
   // --args switch must be present.
   CHECK_LT(i, argc);