Use remove_if to erase parts of a vector. Avoids O(n^2) worst cases.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@181150 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Frontend/ASTUnit.cpp b/lib/Frontend/ASTUnit.cpp
index 8fe4baa..8bd5172 100644
--- a/lib/Frontend/ASTUnit.cpp
+++ b/lib/Frontend/ASTUnit.cpp
@@ -1037,16 +1037,17 @@
 
 }
 
-static void checkAndRemoveNonDriverDiags(SmallVectorImpl<StoredDiagnostic> &
-                                                            StoredDiagnostics) {
+static bool isNonDriverDiag(const StoredDiagnostic &StoredDiag) {
+  return StoredDiag.getLocation().isValid();
+}
+
+static void
+checkAndRemoveNonDriverDiags(SmallVectorImpl<StoredDiagnostic> &StoredDiags) {
   // Get rid of stored diagnostics except the ones from the driver which do not
   // have a source location.
-  for (unsigned I = 0; I < StoredDiagnostics.size(); ++I) {
-    if (StoredDiagnostics[I].getLocation().isValid()) {
-      StoredDiagnostics.erase(StoredDiagnostics.begin()+I);
-      --I;
-    }
-  }
+  StoredDiags.erase(
+      std::remove_if(StoredDiags.begin(), StoredDiags.end(), isNonDriverDiag),
+      StoredDiags.end());
 }
 
 static void checkAndSanitizeDiags(SmallVectorImpl<StoredDiagnostic> &