Address review comments.

# Conflicts:
#	Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraph.swift

Author: David Ungar

Sources/SwiftDriver/IncrementalCompilation/ModuleDependencyGraph.swift

@@ -207,10 +207,9 @@ extension ModuleDependencyGraph {
     let diags = info.diagnosticEngine
     var allFound = true
     for input in info.inputFiles {
-      if let source = ofm.getDependencySource(for: input, diagnosticEngine: diags) {
+      if let source = ofm.dependencySource(for: input, diagnosticEngine: diags) {
         inputDependencySourceMap.addEntry(input, source, for: purpose)
-      }
-      else {
+      } else {
         // Don't break in order to report all failures.
         allFound = false
       }
@@ -219,7 +218,7 @@ extension ModuleDependencyGraph {
   }
 }
 extension OutputFileMap {
-  fileprivate func getDependencySource(
+  fileprivate func dependencySource(
     for sourceFile: TypedVirtualPath,
     diagnosticEngine: DiagnosticsEngine
   ) -> DependencySource? {
@@ -343,8 +342,7 @@ extension ModuleDependencyGraph {
   ) -> TransitivelyInvalidatedInputSet? {
     var invalidatedInputs = TransitivelyInvalidatedInputSet()
     for invalidatedSwiftDeps in collectSwiftDepsUsingInvalidated(nodes: directlyInvalidatedNodes) {
-      guard let invalidatedInput = getNeededInput(for: invalidatedSwiftDeps)
-      else {
+      guard let invalidatedInput = input(neededFor: invalidatedSwiftDeps) else {
         return nil
       }
       invalidatedInputs.insert(invalidatedInput)