Update HTTP/2 DATA frame padding to 0x00.

Use 0x00 rather than 0x30 ('0') to pad the DATA frame to be comply with the
HTTP/2 spec.

This lands server change 77448497 by raullenchai.

BUG=345769

Review URL: https://codereview.chromium.org/654253004

Cr-Commit-Position: refs/heads/master@{#300234}

net/spdy/spdy_framer.cc

@@ -2314,7 +2314,7 @@ SpdySerializedFrame* SpdyFramer::SerializeData(
     }
     builder.WriteBytes(data_ir.data().data(), data_ir.data().length());
     if (data_ir.padding_payload_len() > 0) {
-      string padding = string(data_ir.padding_payload_len(), '0');
+      string padding(data_ir.padding_payload_len(), 0);
       builder.WriteBytes(padding.data(), padding.length());
     }
     DCHECK_EQ(size_with_padding, builder.length());

net/spdy/spdy_framer_test.cc

@@ -1638,26 +1638,28 @@ TEST_P(SpdyFramerTest, CreateDataFrame) {
       0x01, 0xf7,                  // Pad length field.
       'h',  'e',  'l',  'l',       // Data
       'o',
-      // Padding of 247 zeros.
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
-      '0',  '0',  '0',  '0',  '0',  '0',  '0',  '0', '0',  '0',  '0',  '0', '0',
+      // Padding of 247 0x00(s).
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
+      0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00,
     };
     const char bytes[] = "hello";
 
@@ -1698,8 +1700,8 @@ TEST_P(SpdyFramerTest, CreateDataFrame) {
       0x01, 0x07,                  // Pad length field.
       'h',  'e',  'l',  'l',       // Data
       'o',
-      '0',  '0',  '0',  '0',       // Padding
-      '0',  '0',  '0'
+      0x00,  0x00,  0x00,  0x00,   // Padding
+      0x00,  0x00,  0x00
     };
     const char bytes[] = "hello";