[clangd] Remove 'using namespace llvm' from .cpp files. NFC

The new guideline is to qualify with 'llvm::' explicitly both in
'.h' and '.cpp' files. This simplifies moving the code between
header and source files and is easier to keep consistent.

llvm-svn: 350531
diff --git a/clang-tools-extra/clangd/FSProvider.cpp b/clang-tools-extra/clangd/FSProvider.cpp
index 99e7596..794bb82 100644
--- a/clang-tools-extra/clangd/FSProvider.cpp
+++ b/clang-tools-extra/clangd/FSProvider.cpp
@@ -15,8 +15,6 @@
 #include "llvm/Support/VirtualFileSystem.h"
 #include <memory>
 
-using namespace llvm;
-
 namespace clang {
 namespace clangd {
 
@@ -28,9 +26,9 @@
   explicit VolatileFileSystem(llvm::IntrusiveRefCntPtr<FileSystem> FS)
       : ProxyFileSystem(std::move(FS)) {}
 
-  llvm::ErrorOr<std::unique_ptr<vfs::File>>
-  openFileForRead(const Twine &InPath) override {
-    SmallString<128> Path;
+  llvm::ErrorOr<std::unique_ptr<llvm::vfs::File>>
+  openFileForRead(const llvm::Twine &InPath) override {
+    llvm::SmallString<128> Path;
     InPath.toVector(Path);
 
     auto File = getUnderlyingFS().openFileForRead(Path);
@@ -38,28 +36,30 @@
       return File;
     // Try to guess preamble files, they can be memory-mapped even on Windows as
     // clangd has exclusive access to those.
-    StringRef FileName = llvm::sys::path::filename(Path);
+    llvm::StringRef FileName = llvm::sys::path::filename(Path);
     if (FileName.startswith("preamble-") && FileName.endswith(".pch"))
       return File;
     return std::unique_ptr<VolatileFile>(new VolatileFile(std::move(*File)));
   }
 
 private:
-  class VolatileFile : public vfs::File {
+  class VolatileFile : public llvm::vfs::File {
   public:
-    VolatileFile(std::unique_ptr<vfs::File> Wrapped)
+    VolatileFile(std::unique_ptr<llvm::vfs::File> Wrapped)
         : Wrapped(std::move(Wrapped)) {
       assert(this->Wrapped);
     }
 
     virtual llvm::ErrorOr<std::unique_ptr<llvm::MemoryBuffer>>
-    getBuffer(const Twine &Name, int64_t FileSize, bool RequiresNullTerminator,
-              bool /*IsVolatile*/) override {
+    getBuffer(const llvm::Twine &Name, int64_t FileSize,
+              bool RequiresNullTerminator, bool /*IsVolatile*/) override {
       return Wrapped->getBuffer(Name, FileSize, RequiresNullTerminator,
                                 /*IsVolatile=*/true);
     }
 
-    llvm::ErrorOr<vfs::Status> status() override { return Wrapped->status(); }
+    llvm::ErrorOr<llvm::vfs::Status> status() override {
+      return Wrapped->status();
+    }
     llvm::ErrorOr<std::string> getName() override { return Wrapped->getName(); }
     std::error_code close() override { return Wrapped->close(); }
 
@@ -77,7 +77,7 @@
 #ifdef _WIN32
   return new VolatileFileSystem(vfs::getRealFileSystem());
 #else
-  return vfs::getRealFileSystem();
+  return llvm::vfs::getRealFileSystem();
 #endif
 }
 } // namespace clangd