SourceManager: Use setMainFileID() consistently

Eliminate createMainFileID() / createMainFileIDForMemBuffer() utility
functions. These didn't add much convenience and conflated two distinct
operations.

This change makes things easier to follow by providing a consistent interface
and getting rid of a bunch of cast-to-voids.

llvm-svn: 209266
diff --git a/clang/lib/Frontend/CompilerInstance.cpp b/clang/lib/Frontend/CompilerInstance.cpp
index 9e07e74..822b44e 100644
--- a/clang/lib/Frontend/CompilerInstance.cpp
+++ b/clang/lib/Frontend/CompilerInstance.cpp
@@ -621,7 +621,7 @@
     Kind = Input.isSystem() ? SrcMgr::C_System : SrcMgr::C_User;
 
   if (Input.isBuffer()) {
-    SourceMgr.createMainFileIDForMemBuffer(Input.getBuffer(), Kind);
+    SourceMgr.setMainFileID(SourceMgr.createFileID(Input.getBuffer(), Kind));
     assert(!SourceMgr.getMainFileID().isInvalid() &&
            "Couldn't establish MainFileID!");
     return true;
@@ -655,7 +655,8 @@
       }
     }
 
-    SourceMgr.createMainFileID(File, Kind);
+    SourceMgr.setMainFileID(
+        SourceMgr.createFileID(File, SourceLocation(), Kind));
   } else {
     std::unique_ptr<llvm::MemoryBuffer> SB;
     if (llvm::error_code ec = llvm::MemoryBuffer::getSTDIN(SB)) {
@@ -664,7 +665,8 @@
     }
     const FileEntry *File = FileMgr.getVirtualFile(SB->getBufferIdentifier(),
                                                    SB->getBufferSize(), 0);
-    SourceMgr.createMainFileID(File, Kind);
+    SourceMgr.setMainFileID(
+        SourceMgr.createFileID(File, SourceLocation(), Kind));
     SourceMgr.overrideFileContents(File, SB.release());
   }