[DevTools] Show blocked requests in Network panel.

Source/devtools/protocol.json

 {
     "version": { "major": "1", "minor": "1" },
     "domains": [{
         "domain": "Inspector",
         "hidden": true,
         "types": [],
         "commands": [
             {
                 "name": "enable",
                 "description": "Enables inspector domain notifications.",
@@ skipping 1212 matching lines @@
                 "description": "Security details about a request.",
                 "properties": [
                     { "name": "protocol", "type": "string", "description": "Protocol name (e.g. \"TLS 1.2\" or \"QUIC\"." },
                     { "name": "keyExchange", "type": "string", "description": "Key Exchange used by the connection." },
                     { "name": "cipher", "type": "string", "description": "Cipher name." },
                     { "name": "mac", "type": "string", "optional": true, "description": "TLS MAC. Note that AEAD ciphers do not have separate MACs." },
                     { "name": "certificateId", "$ref": "CertificateId", "description": "Certificate ID value." }
                 ]
             },
             {
+                "id": "BlockedReason",
+                "type": "string",
+                "description": "The reason why request was blocked.",
+                "enum": ["csp", "mixed-content", "origin", "inspector", "other"],
+                "hidden": true
+            },
+            {
                 "id": "Response",
                 "type": "object",
                 "description": "HTTP response data.",
                 "properties": [
                     { "name": "url", "type": "string", "description": "Response URL. This URL can be different from CachedResource.url in case of redirect." },
                     { "name": "status", "type": "number", "description": "HTTP response status code." },
                     { "name": "statusText", "type": "string", "description": "HTTP response status text." },
                     { "name": "headers", "$ref": "Headers", "description": "HTTP response headers." },
                     { "name": "headersText", "type": "string", "optional": true, "description": "HTTP response headers text." },
                     { "name": "mimeType", "type": "string", "description": "Resource mimeType as determined by the browser." },
@@ skipping 305 matching lines @@
             },
             {
                 "name": "loadingFailed",
                 "description": "Fired when HTTP request has failed to load.",
                 "parameters": [
                     { "name": "requestId", "$ref": "RequestId", "description": "Request identifier." },
                     { "name": "timestamp", "$ref": "Timestamp", "description": "Timestamp." },
                     { "name": "type", "$ref": "Page.ResourceType", "description": "Resource type." },
                     { "name": "errorText", "type": "string", "description": "User friendly error message." },
                     { "name": "canceled", "type": "boolean", "optional": true, "description": "True if loading was canceled." },
-                    { "name": "blocked", "type": "boolean", "optional": true, "description": "True if loading was blocked by inspector." }
+                    { "name": "blockedReason", "$ref": "BlockedReason", "optional": true, "description": "The reason why loading was blocked, if any.", "hidden": true }
                 ]
             },
             {
                 "name": "webSocketWillSendHandshakeRequest",
                 "description": "Fired when WebSocket is about to initiate handshake.",
                 "parameters": [
                     { "name": "requestId", "$ref": "RequestId", "description": "Request identifier." },
                     { "name": "timestamp", "$ref": "Timestamp", "description": "Timestamp." },
                     { "name": "wallTime", "$ref": "Timestamp", "hidden": true, "description": "UTC Timestamp." },
                     { "name": "request", "$ref": "WebSocketRequest", "description": "WebSocket request data." }
@@ skipping 3659 matching lines @@
                 ],
                 "returns": [
                     { "name": "accessibilityNode", "$ref": "AXNode", "description": "The <code>Accessibility.AXNode</code> for this DOM node, if it exists.", "optional": true }
                 ],
                 "description": "Fetches the accessibility node for this DOM node, if it exists.",
                 "hidden": true
             }
         ]
     }]
 }