GN: Add common header extensions

GN now recognizes most common header file extensions:
*.h, *.hh, *.hpp, *.hxx

These are all used inside the chromium repository.
This change makes "gn check" more robust.

R=brettw@chromium.org
BUG=

Review-Url: https://codereview.chromium.org/1933323002
Cr-Original-Commit-Position: refs/heads/master@{#391056}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: cc00b4093699e76fb09489ede68c1eb3fb4b0db7
diff --git a/tools/gn/source_file_type.cc b/tools/gn/source_file_type.cc
index 72b872c..328b2ab 100644
--- a/tools/gn/source_file_type.cc
+++ b/tools/gn/source_file_type.cc
@@ -11,7 +11,8 @@
   base::StringPiece extension = FindExtension(&file.value());
   if (extension == "cc" || extension == "cpp" || extension == "cxx")
     return SOURCE_CPP;
-  if (extension == "h")
+  if (extension == "h" || extension == "hpp" || extension == "hxx" ||
+      extension == "hh")
     return SOURCE_H;
   if (extension == "c")
     return SOURCE_C;