clang/win: Build with some more clang warnings enabled.

build/config/compiler/BUILD.gn

Index: build/config/compiler/BUILD.gn
diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 75c3fe53da3afc2a77d7f27e63b8139a6484a47c..ad4d59d3976020615cf69f12b3c136e996dcc901 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -800,9 +800,7 @@ if (is_win) {
       # TODO(hans): Make this list shorter eventually, http://crbug.com/504657
       "-Qunused-arguments",  # http://crbug.com/504658
       "-Wno-c++11-compat-deprecated-writable-strings",  # http://crbug.com/504659
-      "-Wno-deprecated-declarations",  # http://crbug.com/504660
       "-Wno-empty-body",  # http://crbug.com/504661
-      "-Wno-enum-conversion",  # http://crbug.com/504662
       "-Wno-extra-tokens",  # http://crbug.com/504663
       "-Wno-ignored-attributes",  # http://crbug.com/504695
       "-Wno-incompatible-pointer-types",  # http://crbug.com/504696
@@ -815,7 +813,6 @@ if (is_win) {
       "-Wno-overloaded-virtual",  # http://crbug.com/505301
       "-Wno-pointer-sign",  # http://crbug.com/505303
       "-Wno-reorder",  # http://crbug.com/505304
-      "-Wno-return-type-c-linkage",  # http://crbug.com/505305
       "-Wno-sometimes-uninitialized",  # http://crbug.com/505307
       "-Wno-switch",  # http://crbug.com/505308
       "-Wno-unknown-pragmas",  # http://crbug.com/505314