gn win: Enable exceptions for pdfium build

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 09f8e6270904dfcf32a5ca15d05c00a8e1ae916c..17e6cb61cdec3bb746bf44a550d525877acbc99d 100644
--- a/build/config/compiler/BUILD.gn
+++ b/build/config/compiler/BUILD.gn
@@ -54,12 +54,6 @@ config("compiler") {
       "/GS",  # Enable buffer security checking.
       "/FS",  # Preserve previous PDB behavior.
     ]
-    if (is_component_build) {
-      cflags += [
-        "/EHsc",  # Assume C functions can't throw exceptions and don't catch
-                  # structured exceptions (only C++ ones).
-      ]
-    }
   } else {
     # Common GCC compiler flags setup.
     # --------------------------------
@@ -353,9 +347,6 @@ config("runtime_library") {
   } else {
     # Static CRT.
     if (is_win) {
-      # We don't use exceptions, and when we link statically we can just get
-      # rid of them entirely.
-      defines += [ "_HAS_EXCEPTIONS=0" ]
       if (is_debug) {
         cflags += [ "/MTd" ]
       } else {
@@ -563,6 +554,27 @@ config("no_rtti") {
   }
 }
 
+# Exceptions -------------------------------------------------------------------
+
+# Some code requires turning exceptions back on (off is the default).
+
+config("no_exceptions") {
+  if (is_win) {
+    defines = [ "_HAS_EXCEPTIONS=0" ]
+  } else if (is_posix) {
+    cflags_cc = [ "-fno-exceptions" ]
+  }
+}
+
+config("exceptions") {
+  if (is_win) {
+    cflags = [
+      "/EHsc",  # Assume C functions can't throw exceptions and don't catch
+                # structured exceptions (only C++ ones).
+    ]
+  }
+}
+
 # Warnings ---------------------------------------------------------------------
 #
 # This is where we disable various warnings that we've decided aren't