feat(page): move page.pdf to protocol streams (#4587)

This lets transferring massive PDF files over the protocol.

Fix #4563

lib/Page.js

@@ -924,6 +924,7 @@ class Page extends EventEmitter {
     const marginRight = convertPrintParameterToInches(margin.right) || 0;
 
     const result = await this._client.send('Page.printToPDF', {
+      transferMode: 'ReturnAsStream',
       landscape,
       displayHeaderFooter,
       headerTemplate,
@@ -939,10 +940,7 @@ class Page extends EventEmitter {
       pageRanges,
       preferCSSPageSize
     });
-    const buffer = Buffer.from(result.data, 'base64');
+    return await helper.readProtocolStream(this._client, result.stream, path);
-    if (path !== null)
-      await writeFileAsync(path, buffer);
-    return buffer;
   }
 
   /**

lib/Tracing.js

@@ -14,11 +14,6 @@
  * limitations under the License.
  */
 const {helper, assert} = require('./helper');
-const fs = require('fs');
-
-const openAsync = helper.promisify(fs.open);
-const writeAsync = helper.promisify(fs.write);
-const closeAsync = helper.promisify(fs.close);
 
 class Tracing {
   /**
@@ -66,40 +61,12 @@ class Tracing {
     let fulfill;
     const contentPromise = new Promise(x => fulfill = x);
     this._client.once('Tracing.tracingComplete', event => {
-      this._readStream(event.stream, this._path).then(fulfill);
+      helper.readProtocolStream(this._client, event.stream, this._path).then(fulfill);
     });
     await this._client.send('Tracing.end');
     this._recording = false;
     return contentPromise;
   }
-
-  /**
-   * @param {string} handle
-   * @param {?string} path
-   */
-  async _readStream(handle, path) {
-    let eof = false;
-    let file;
-    if (path)
-      file = await openAsync(path, 'w');
-    const bufs = [];
-    while (!eof) {
-      const response = await this._client.send('IO.read', {handle});
-      eof = response.eof;
-      bufs.push(Buffer.from(response.data));
-      if (path)
-        await writeAsync(file, response.data);
-    }
-    if (path)
-      await closeAsync(file);
-    await this._client.send('IO.close', {handle});
-    let resultBuffer = null;
-    try {
-      resultBuffer = Buffer.concat(bufs);
-    } finally {
-      return resultBuffer;
-    }
-  }
 }
 
 module.exports = Tracing;

lib/helper.js

@@ -14,8 +14,8 @@
  * limitations under the License.
  */
 const {TimeoutError} = require('./Errors');
-
 const debugError = require('debug')(`puppeteer:error`);
+const fs = require('fs');
 
 class Helper {
   /**
@@ -221,8 +221,43 @@ class Helper {
       clearTimeout(timeoutTimer);
     }
   }
+
+  /**
+   * @param {!Puppeteer.CDPSession} client
+   * @param {string} handle
+   * @param {?string} path
+   * @return {!Promise<!Buffer>}
+   */
+  static async readProtocolStream(client, handle, path) {
+    let eof = false;
+    let file;
+    if (path)
+      file = await openAsync(path, 'w');
+    const bufs = [];
+    while (!eof) {
+      const response = await client.send('IO.read', {handle});
+      eof = response.eof;
+      const buf = Buffer.from(response.data, response.base64Encoded ? 'base64' : undefined);
+      bufs.push(buf);
+      if (path)
+        await writeAsync(file, buf);
+    }
+    if (path)
+      await closeAsync(file);
+    await client.send('IO.close', {handle});
+    let resultBuffer = null;
+    try {
+      resultBuffer = Buffer.concat(bufs);
+    } finally {
+      return resultBuffer;
+    }
+  }
 }
 
+const openAsync = Helper.promisify(fs.open);
+const writeAsync = Helper.promisify(fs.write);
+const closeAsync = Helper.promisify(fs.close);
+
 /**
  * @param {*} value
  * @param {string=} message