Chromium roll (https://codereview.chromium.org/976353002)

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 5cf0331c87d64bb16123d72e0993db9c448424b1..43971510dbe6341bafce5e079ec4291571dcffa0 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -48,6 +48,13 @@ declare_args() {
   # http://gcc.gnu.org/wiki/DebugFission
   use_debug_fission =
       !is_win && use_gold && linux_use_bundled_binutils && !use_ccache
+
+  if (is_win) {
+    # Whether the VS xtree header has been patched to disable warning 4702. If
+    # it has, then we don't need to disable 4702 (unreachable code warning).
+    # The patch is preapplied to the internal toolchain and hence all bots.
+    msvs_xtree_patched = false
+  }
 }
 
 # default_include_dirs ---------------------------------------------------------
@@ -295,12 +302,23 @@ config("compiler") {
             "-mips32r2",
             "-Wa,-mips32r2",
           ]
+          if (mips_float_abi == "hard" && mips_fpu_mode != "") {
+            cflags += [ "-m$mips_fpu_mode" ]
+          }
         } else if (mips_arch_variant == "r1") {
           cflags += [
             "-mips32",
             "-Wa,-mips32",
           ]
         }
+
+        if (mips_dsp_rev == 1) {
+          cflags += [ "-mdsp" ]
+        } else if (mips_dsp_rev == 2) {
+          cflags += [ "-mdspr2" ]
+        }
+
+        cflags += [ "-m${mips_float_abi}-float" ]
       }
     } else if (current_cpu == "mips64el") {
       # Don't set the compiler flags for the WebView build. These will come
@@ -709,6 +727,7 @@ config("default_warnings") {
   if (is_win) {
     cflags = [
       "/WX",  # Treat warnings as errors.
+
       # Warnings permanently disabled:
 
       # TODO(GYP) The GYP build doesn't have this globally enabled but disabled
@@ -763,6 +782,7 @@ config("default_warnings") {
       # have to turn off this warning (and be careful about how object
       # destruction happens in such cases).
       "/wd4611",
+
       # Warnings to evaluate and possibly fix/reenable later:
 
       "/wd4100",  # Unreferenced formal function parameter.
@@ -775,6 +795,14 @@ config("default_warnings") {
       "/wd4610",  # Class can never be instantiated, constructor required.
       "/wd4996",  # Deprecated function warning.
     ]
+
+    # VS xtree header file needs to be patched or 4702 (unreachable code
+    # warning) is reported if _HAS_EXCEPTIONS=0. Disable the warning if xtree is
+    # not patched.
+    if (!msvs_xtree_patched &&
+        exec_script("../../win_is_xtree_patched.py", [], "value") == 0) {
+      cflags += [ "/wd4702" ]  # Unreachable code.
+    }
   } else {
     # Common GCC warning setup.
     cflags = [