Copying gyp warning disables to gn for VS 2015 64-bit

gyp 64-bit builds with VS 2015, but gn 64-bit builds do not,
because some warnings are disabled for gyp builds but not gn builds.
This change makes the gn settings consistent enough to let gn 64-bit
VS 2015 builds work.

- build\config\compiler\BUILD.gn - disabling of C4312 copied from
build\common.gypi
- third_party/libxml/BUILD.gn and third_party/libxslt/BUILD.gn -
disabling of C4267 and C4311 copied from libxml.gyp and libxslt.gyp
files. Disabling of C4101 was *removed* from libxml\BUILD.gn for
consistency and because it isn't needed anymore
- third_party/mesa/BUILD.gn - disabling of C4311 copied from mesa.gyp

R=scottmg@chromium.org
BUG=440500

Review URL: https://codereview.chromium.org/1561913002

Cr-Commit-Position: refs/heads/master@{#367944}

5 files changed, 23 insertions, 9 deletions

diff --git a/build/config/compiler/BUILD.gn b/build/config/compiler/BUILD.gn
index 9f05d76..d52185a 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -750,11 +750,17 @@ config("default_warnings") {
     ]
 
     if (visual_studio_version == "2015") {
-      # VC++ 2015 changes 32-bit size_t truncation warnings from 4244 to 4267.
-      # Example: short TruncTest(size_t x) { return x; }
-      # Since we already disable 4244 we need to disable 4267 during migration.
-      # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
-      cflags += [ "/wd4267" ]
+      cflags += [
+        # VC++ 2015 changes 32-bit size_t truncation warnings from 4244 to 4267.
+        # Example: short TruncTest(size_t x) { return x; }
+        # Since we disable 4244 we need to disable 4267 during migration.
+        # TODO(jschuh): crbug.com/167187 fix size_t to int truncations.
+        "/wd4267",
+
+        # C4312 is a VS 2015 64-bit warning for integer to larger pointer.
+        # TODO(brucedawson): fix warnings, crbug.com/554200
+        "/wd4312",
+      ]
     }
 
     # VS xtree header file needs to be patched or 4702 (unreachable code
diff --git a/third_party/libxml/BUILD.gn b/third_party/libxml/BUILD.gn
index 5e633c0..70b66ab 100644
--- a/third_party/libxml/BUILD.gn
+++ b/third_party/libxml/BUILD.gn
@@ -28,7 +28,8 @@ config("libxml_warnings") {
   if (is_win) {
     cflags_c = [
       "/wd4018",  # Signed/unsigned mismatch in comparison.
-      "/wd4101",  # Unreferenced local variable.
+      "/wd4267",  # TODO(brucedawson): http://crbug.com/554200 fix C4267
+      "/wd4311",  # and C4311 warnings.
     ]
   }
   if (is_clang) {
diff --git a/third_party/libxslt/BUILD.gn b/third_party/libxslt/BUILD.gn
index 3f27c5de5..6e8dcc9 100644
--- a/third_party/libxslt/BUILD.gn
+++ b/third_party/libxslt/BUILD.gn
@@ -86,7 +86,13 @@ static_library("libxslt") {
     include_dirs = [ "linux" ]
   } else if (is_win) {
     include_dirs = [ "win32" ]
-    cflags += [ "/wd4267" ]  # size_t to int.
+    cflags += [
+      "/wd4267",  # size_t to int.
+
+      # TODO(brucedawson): http://crbug.com/554200 4311 is a VS
+      # 2015 64-bit warning for pointer truncation
+      "/wd4311",
+    ]
   } else if (is_mac) {
     include_dirs = [ "mac" ]
   }
diff --git a/third_party/libxslt/libxslt.gyp b/third_party/libxslt/libxslt.gyp
index 19ea0b1..fc6ffc4 100644
--- a/third_party/libxslt/libxslt.gyp
+++ b/third_party/libxslt/libxslt.gyp
@@ -109,8 +109,8 @@
           'msvs_disabled_warnings': [
             # size_t to int conversion.
             4267,
-            # TODO(brucedawson): http://crbug.com/554200 4311 is a VS
-            # 2015 64-bit warning for pointer truncation
+            # TODO(brucedawson): http://crbug.com/554200 4311 is a
+            # VS 2015 64-bit warning for pointer truncation
             4311,
           ],
           'variables': {
diff --git a/third_party/mesa/BUILD.gn b/third_party/mesa/BUILD.gn
index 6ae815d..a6fdb11 100644
--- a/third_party/mesa/BUILD.gn
+++ b/third_party/mesa/BUILD.gn
@@ -141,6 +141,7 @@ config("mesa_internal_warnings") {
       "/wd4305",  # Truncation from int to float.
       "/wd4334",  # Result of 32-bit shift implicitly converted to 64 bits.
       "/wd4345",  # POD-type default initializers.
+      "/wd4311",  # Pointer truncation TODO(brucedawson): http://crbug.com/554200
     ]
   }
 }