gn win: Various toolchain fixes to get compile working

build/config/win/BUILD.gn

Index: build/config/win/BUILD.gn
diff --git a/build/config/win/BUILD.gn b/build/config/win/BUILD.gn
index 58e310f423993adc6058c1315c925e2163202108..f6230648441a55f99926567f2c808f86b4b674e7 100644
--- a/build/config/win/BUILD.gn
+++ b/build/config/win/BUILD.gn
@@ -16,19 +16,10 @@ config("sdk") {
     "NTDDI_VERSION=0x06030000",
     "PSAPI_VERSION=1",
     "WIN32",
+    "_SECURE_ATL",
   ]
 
   include_dirs = system_include_dirs
-
-  if (is_visual_studio_express) {
-    # https://code.google.com/p/chromium/issues/detail?id=372451#c20
-    # Warning 4702 ("Unreachable code") should be re-enabled once Express users
-    # are updated to VS2013 Update 2.
-    cflags = [ "/wd4702" ]
-  } else {
-    # Only supported on non-Express versions.
-    defines += [ "_SECURE_ATL" ]
-  }
 }
 
 # Sets the default Windows build version. This is separated because some
@@ -49,9 +40,6 @@ config("sdk_link") {
       "$visual_studio_path\VC\lib\amd64",
       "$visual_studio_path\VC\atlmfc\lib\amd64",
     ]
-    if (is_visual_studio_express) {
-      lib_dirs += [ "$wdk_path/lib/ATL/amd64" ]
-    }
   } else {
     ldflags = [
       "/MACHINE:X86",
@@ -62,26 +50,10 @@ config("sdk_link") {
       "$visual_studio_path\VC\lib",
       "$visual_studio_path\VC\atlmfc\lib",
     ]
-    if (is_visual_studio_express) {
-      lib_dirs += [ "$wdk_path/lib/ATL/i386" ]
-    }
     if (!is_asan) {
       ldflags += [ "/largeaddressaware" ]
     }
   }
-
-  if (is_visual_studio_express) {
-    # Explicitly required when using the ATL with express.
-    libs = [ "atlthunk.lib" ]
-
-    # ATL 8.0 included in WDK 7.1 makes the linker to generate almost eight
-    # hundred LNK4254 and LNK4078 warnings:
-    #   - warning LNK4254: section 'ATL' (50000040) merged into '.rdata'
-    #     (40000040) with different attributes
-    #   - warning LNK4078: multiple 'ATL' sections found with different
-    #     attributes
-    ldflags += [ "/ignore:4254", "/ignore:4078" ]
-  }
 }
 
 # This default linker setup is provided separately from the SDK setup so