diff --git a/BUILD.gn b/BUILD.gn
index 885c2bb..bdb5dae 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -17,6 +17,7 @@
 
 config("pdfium_common_config") {
   cflags = []
+  cflags_cc = []
   ldflags = []
   include_dirs = [ "." ]
   defines = [
@@ -43,8 +44,168 @@
   if (is_win) {
     # Assume UTF-8 by default to avoid code page dependencies.
     cflags += [ "/utf-8" ]
-    if (msvc_use_sse2 && !is_clang && current_cpu == "x86") {
-      cflags += [ "/arch:SSE2" ]
+
+    if (!is_clang) {
+      cflags += [
+        # Warnings permanently disabled:
+
+        # C4091: 'typedef ': ignored on left of 'X' when no variable is
+        #                    declared.
+        # This happens in a number of Windows headers. Dumb.
+        "/wd4091",
+
+        # C4127: conditional expression is constant
+        # This warning can in theory catch dead code and other problems, but
+        # triggers in far too many desirable cases where the conditional
+        # expression is either set by macros or corresponds some legitimate
+        # compile-time constant expression (due to constant template args,
+        # conditionals comparing the sizes of different types, etc.).  Some of
+        # these can be worked around, but it's not worth it.
+        "/wd4127",
+
+        # C4251: 'identifier' : class 'type' needs to have dll-interface to be
+        #        used by clients of class 'type2'
+        # This is necessary for the shared library build.
+        "/wd4251",
+
+        # C4275:  non dll-interface class used as base for dll-interface class
+        # This points out a potential (but rare) problem with referencing static
+        # fields of a non-exported base, through the base's non-exported inline
+        # functions, or directly. The warning is subtle enough that people just
+        # suppressed it when they saw it, so it's not worth it.
+        "/wd4275",
+
+        # C4312 is a VS 2015 64-bit warning for integer to larger pointer.
+        # TODO(brucedawson): fix warnings, crbug.com/554200
+        "/wd4312",
+
+        # C4324 warns when padding is added to fulfill alignas requirements,
+        # but can trigger in benign cases that are difficult to individually
+        # suppress.
+        "/wd4324",
+
+        # C4351: new behavior: elements of array 'array' will be default
+        #        initialized
+        # This is a silly "warning" that basically just alerts you that the
+        # compiler is going to actually follow the language spec like it's
+        # supposed to, instead of not following it like old buggy versions did.
+        # There's absolutely no reason to turn this on.
+        "/wd4351",
+
+        # C4355: 'this': used in base member initializer list
+        # It's commonly useful to pass |this| to objects in a class' initializer
+        # list.  While this warning can catch real bugs, most of the time the
+        # constructors in question don't attempt to call methods on the passed-in
+        # pointer (until later), and annotating every legit usage of this is
+        # simply more hassle than the warning is worth.
+        "/wd4355",
+
+        # C4503: 'identifier': decorated name length exceeded, name was
+        #        truncated
+        # This only means that some long error messages might have truncated
+        # identifiers in the presence of lots of templates.  It has no effect on
+        # program correctness and there's no real reason to waste time trying to
+        # prevent it.
+        "/wd4503",
+
+        # Warning C4589 says: "Constructor of abstract class ignores
+        # initializer for virtual base class." Disable this warning because it
+        # is flaky in VS 2015 RTM. It triggers on compiler generated
+        # copy-constructors in some cases.
+        "/wd4589",
+
+        # C4611: interaction between 'function' and C++ object destruction is
+        #        non-portable
+        # This warning is unavoidable when using e.g. setjmp/longjmp.  MSDN
+        # suggests using exceptions instead of setjmp/longjmp for C++, but
+        # Chromium code compiles without exception support.  We therefore have to
+        # use setjmp/longjmp for e.g. JPEG decode error handling, which means we
+        # 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.
+        "/wd4121",  # Alignment of a member was sensitive to packing.
+        "/wd4244",  # Conversion: possible loss of data.
+        "/wd4505",  # Unreferenced local function has been removed.
+        "/wd4510",  # Default constructor could not be generated.
+        "/wd4512",  # Assignment operator could not be generated.
+        "/wd4610",  # Class can never be instantiated, constructor required.
+        "/wd4838",  # Narrowing conversion. Doesn't seem to be very useful.
+        "/wd4995",  # 'X': name was marked as #pragma deprecated
+        "/wd4996",  # Deprecated function warning.
+
+        # These are variable shadowing warnings that are new in VS2015. We
+        # should work through these at some point -- they may be removed from
+        # the RTM release in the /W4 set.
+        "/wd4456",
+        "/wd4457",
+        "/wd4458",
+        "/wd4459",
+
+        # All of our compilers support the extensions below.
+        "/wd4200",  # nonstandard extension used: zero-sized array in
+                    # struct/union
+        "/wd4201",  # nonstandard extension used: nameless struct/union
+        "/wd4204",  # nonstandard extension used : non-constant aggregate
+                    # initializer
+
+        "/wd4221",  # nonstandard extension used : 'identifier' : cannot be
+                    # initialized using address of automatic variable
+
+        # http://crbug.com/588506 - Conversion suppressions waiting on Clang
+        # -Wconversion.
+        "/wd4245",  # 'conversion' : conversion from 'type1' to 'type2',
+                    # signed/unsigned mismatch
+
+        "/wd4267",  # 'var' : conversion from 'size_t' to 'type', possible loss
+                    # of
+                    # data
+
+        "/wd4305",  # 'identifier' : truncation from 'type1' to 'type2'
+        "/wd4389",  # 'operator' : signed/unsigned mismatch
+
+        "/wd4702",  # unreachable code
+
+        # http://crbug.com/848979 - MSVC is more conservative than Clang with
+        # regards to variables initialized and consumed in different branches.
+        "/wd4701",  # Potentially uninitialized local variable 'name' used
+        "/wd4703",  # Potentially uninitialized local pointer variable 'name'
+                    # used
+
+        # http://crbug.com/848979 - Remaining Clang permitted warnings.
+        "/wd4661",  # 'identifier' : no suitable definition provided for
+                    # explicit
+                    # template instantiation request
+
+        "/wd4706",  # assignment within conditional expression
+                    # MSVC is stricter and requires a boolean expression.
+
+        "/wd4715",  # 'function' : not all control paths return a value'
+                    # MSVC does not analyze switch (enum) for completeness.
+      ]
+
+      cflags_cc += [
+        # Allow "noexcept" annotations even though we compile with exceptions
+        # disabled.
+        "/wd4577",
+      ]
+
+      if (current_cpu == "x86") {
+        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",
+        ]
+
+        if (msvc_use_sse2) {
+          cflags += [ "/arch:SSE2" ]
+        }
+      }
     }
   }