Improve error messages and reporting in GN

tools/gn/builder_unittest.cc

 // Copyright (c) 2013 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "testing/gtest/include/gtest/gtest.h"
 #include "tools/gn/builder.h"
 #include "tools/gn/loader.h"
 #include "tools/gn/target.h"
 #include "tools/gn/test_with_scope.h"
 #include "tools/gn/toolchain.h"
 
 namespace {
 
 class MockLoader : public Loader {
  public:
   MockLoader() {
   }
 
   // Loader implementation:
   virtual void Load(const SourceFile& file,
+                    const LocationRange& origin,
                     const Label& toolchain_name) OVERRIDE {
     files_.push_back(file);
   }
   virtual void ToolchainLoaded(const Toolchain* toolchain) OVERRIDE {
   }
   virtual Label GetDefaultToolchain() const OVERRIDE {
     return Label();
   }
   virtual const Settings* GetToolchainSettings(
       const Label& label) const OVERRIDE {
@@ skipping 175 matching lines @@
   a->set_output_type(Target::EXECUTABLE);
   builder_->ItemDefined(scoped_ptr<Item>(a));
 
   // A should have the generate bit set since it's in the default toolchain.
   BuilderRecord* a_record = builder_->GetRecord(a_label);
   EXPECT_TRUE(a_record->should_generate());
 
   // It should have gotten pushed to B.
   EXPECT_TRUE(b_record->should_generate());
 }