Index: lib/Format/Format.cpp
===================================================================
--- lib/Format/Format.cpp	(revision 221760)
+++ lib/Format/Format.cpp	(working copy)
@@ -574,6 +574,12 @@
 
 namespace {
 
+bool isExternCBlock(const AnnotatedLine &Line) {
+  return Line.First->is(tok::kw_extern) && Line.First->Next &&
+         Line.First->Next->isStringLiteral() && Line.First->Next->Next &&
+         Line.First->Next->Next->is(tok::l_brace);
+}
+
 class NoColumnLimitFormatter {
 public:
   NoColumnLimitFormatter(ContinuationIndenter *Indenter) : Indenter(Indenter) {}
@@ -785,7 +791,8 @@
       Tok->SpacesRequiredBefore = 0;
       Tok->CanBreakBefore = true;
       return 1;
-    } else if (Limit != 0 && Line.First->isNot(tok::kw_namespace)) {
+    } else if (Limit != 0 && Line.First->isNot(tok::kw_namespace) &&
+               !isExternCBlock(Line)) {
       // We don't merge short records.
       if (Line.First->isOneOf(tok::kw_class, tok::kw_union, tok::kw_struct))
         return 0;
@@ -1069,7 +1076,8 @@
     // Remove empty lines after "{".
     if (!Style.KeepEmptyLinesAtTheStartOfBlocks && PreviousLine &&
         PreviousLine->Last->is(tok::l_brace) &&
-        PreviousLine->First->isNot(tok::kw_namespace))
+        PreviousLine->First->isNot(tok::kw_namespace) &&
+        !isExternCBlock(*PreviousLine))
       Newlines = 1;
 
     // Insert extra new line before access specifiers.
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp	(revision 221760)
+++ unittests/Format/FormatTest.cpp	(working copy)
@@ -187,7 +187,7 @@
                    "\n"
                    "};"));
 
-  // Don't remove empty lines at the start of namespaces.
+  // Don't remove empty lines at the start of namespaces or extern "C" blocks.
   EXPECT_EQ("namespace N {\n"
             "\n"
             "int i;\n"
@@ -197,7 +197,30 @@
                    "int    i;\n"
                    "}",
                    getGoogleStyle()));
+  EXPECT_EQ("extern \"C\" {\n"
+            "\n"
+            "int i;\n"
+            "}",
+            format("extern \"C\" {\n"
+                   "\n"
+                   "int    i;\n"
+                   "}",
+                   getGoogleStyle()));
 
+  // ...but do keep inlining and removing empty lines for non-block extern "C"
+  // functions.
+  verifyFormat("extern \"C\" int f() { return 42; }", getGoogleStyle());
+  EXPECT_EQ("extern \"C\" int f() {\n"
+            "  int i = 42;\n"
+            "  return i;\n"
+            "}",
+            format("extern \"C\" int f() {\n"
+                   "\n"
+                   "  int i = 42;\n"
+                   "  return i;\n"
+                   "}",
+                   getGoogleStyle()));
+
   // Remove empty lines at the beginning and end of blocks.
   EXPECT_EQ("void f() {\n"
             "\n"