Enable parallel compiles. This speeds up builds on 4-processor systems by about 30%, and at least doesn't hurt 2-processor systems.

Review URL: http://codereview.chromium.org/16521

git-svn-id: http://src.chromium.org/svn/trunk/src/build@7573 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

internal/essential.vsprops

@@ -9,6 +9,7 @@
 	>
 	<Tool
 		Name="VCCLCompilerTool"
+		AdditionalOptions="/MP"
 		AdditionalIncludeDirectories="$(SolutionDir)..;$(SDKIncludes)"
 		PreprocessorDefinitions="_WIN32_WINNT=0x0600;WINVER=0x0600;WIN32;_WINDOWS;_HAS_EXCEPTIONS=0;NOMINMAX;_CRT_RAND_S;CERT_CHAIN_PARA_HAS_EXTRA_FIELDS;WIN32_LEAN_AND_MEAN;_SECURE_ATL;_HAS_TR1=0"
 		MinimalRebuild="false"