[clangd] cleanup: unify the implemenation of checking a location is inside main file.

Summary: We have variant implementations in the codebase, this patch unifies them.

Reviewers: ilya-biryukov, kadircet

Subscribers: MaskRay, jkorous, arphaman, cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D64915

llvm-svn: 366541
diff --git a/clang-tools-extra/clangd/Headers.cpp b/clang-tools-extra/clangd/Headers.cpp
index 877301e..7caaeba 100644
--- a/clang-tools-extra/clangd/Headers.cpp
+++ b/clang-tools-extra/clangd/Headers.cpp
@@ -35,7 +35,7 @@
                           llvm::StringRef /*RelativePath*/,
                           const Module * /*Imported*/,
                           SrcMgr::CharacteristicKind FileKind) override {
-    if (SM.isWrittenInMainFile(HashLoc)) {
+    if (isInsideMainFile(HashLoc, SM)) {
       Out->MainFileIncludes.emplace_back();
       auto &Inc = Out->MainFileIncludes.back();
       Inc.R = halfOpenToRange(SM, FilenameRange);