implement GetProcessExecutablePath() on OpenBSD and start using it

base/base_paths_linux.cc

Index: base/base_paths_linux.cc
diff --git a/base/base_paths_linux.cc b/base/base_paths_linux.cc
index b082eb3b3d71e6811ed385541df2df7268d1bb0e..4fa04d825b7457a84b239f7886faf164b1fc1521 100644
--- a/base/base_paths_linux.cc
+++ b/base/base_paths_linux.cc
@@ -68,7 +68,11 @@ bool PathProviderPosix(int key, FilePath* result) {
       return true;
 #elif defined(OS_OPENBSD)
       // There is currently no way to get the executable path on OpenBSD
-      *result = FilePath("/usr/local/chrome/chrome");
+      char *cpath;
+      if ((cpath = getenv("CHROME_EXE_PATH")) != NULL)
+        *result = FilePath(cpath);
+      else
+        *result = FilePath("/usr/local/chrome/chrome");
       return true;
 #endif
     }