Add experimental code behind a flag for Content Size Policy

content/public/common/content_switches.cc

Index: content/public/common/content_switches.cc
diff --git a/content/public/common/content_switches.cc b/content/public/common/content_switches.cc
index 7b9aba69b55fb7ba2d714c6f61b97fc67086e92d..e3a865dd3a63859750c627a61f72b5398d25cafc 100644
--- a/content/public/common/content_switches.cc
+++ b/content/public/common/content_switches.cc
@@ -873,6 +873,9 @@ const char kEnableNativeGpuMemoryBuffers[] = "enable-native-gpu-memory-buffers";
 // Texture target for CHROMIUM_image backed content textures.
 const char kContentImageTextureTarget[] = "content-image-texture-target";
 
+// The max total content size a cross-site subframe can use. In bytes.
+const char kContentSizePolicy[] = "content-size-policy";
+
 // Texture target for CHROMIUM_image backed video frame textures.
 const char kVideoImageTextureTarget[] = "video-image-texture-target";