rtc::Buffer: Remove backwards compatibility band-aids

This CL makes two changes to rtc::Buffer that have had to wait for
Chromium's use of it to be modernized:

  1. Change default return type of rtc::Buffer::data() from char* to
     uint8_t*. uint8_t is a more natural type for bytes, and won't
     accidentally convert to a string. (Chromium previously expected
     the default return type to be char, which is why
     rtc::Buffer::data() initially got char as default return type in
     9478437f, but that's been fixed now.)

  2. Stop accepting void* inputs in constructors and methods. While
     this is convenient, it's also dangerous since any pointer type
     will implicitly convert to void*.

(This was previously committed (9e1a6d7c) but had to be reverted
(cbf09274) because Chromium on Android wasn't quite ready for it).

TBR=tommi@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/47109004

Cr-Commit-Position: refs/heads/master@{#9132}
diff --git a/webrtc/base/buffer_unittest.cc b/webrtc/base/buffer_unittest.cc
index 963209c..f1ae6b8 100644
--- a/webrtc/base/buffer_unittest.cc
+++ b/webrtc/base/buffer_unittest.cc
@@ -137,11 +137,11 @@
 
 TEST(BufferTest, TestMoveConstruct) {
   Buffer buf1(kTestData, 3, 40);
-  const uint8_t* data = buf1.data<uint8_t>();
+  const uint8_t* data = buf1.data();
   Buffer buf2(buf1.Pass());
   EXPECT_EQ(buf2.size(), 3u);
   EXPECT_EQ(buf2.capacity(), 40u);
-  EXPECT_EQ(buf2.data<uint8_t>(), data);
+  EXPECT_EQ(buf2.data(), data);
   buf1.Clear();
   EXPECT_EQ(buf1.size(), 0u);
   EXPECT_EQ(buf1.capacity(), 0u);
@@ -150,12 +150,12 @@
 
 TEST(BufferTest, TestMoveAssign) {
   Buffer buf1(kTestData, 3, 40);
-  const uint8_t* data = buf1.data<uint8_t>();
+  const uint8_t* data = buf1.data();
   Buffer buf2(kTestData);
   buf2 = buf1.Pass();
   EXPECT_EQ(buf2.size(), 3u);
   EXPECT_EQ(buf2.capacity(), 40u);
-  EXPECT_EQ(buf2.data<uint8_t>(), data);
+  EXPECT_EQ(buf2.data(), data);
   buf1.Clear();
   EXPECT_EQ(buf1.size(), 0u);
   EXPECT_EQ(buf1.capacity(), 0u);
@@ -165,16 +165,16 @@
 TEST(BufferTest, TestSwap) {
   Buffer buf1(kTestData, 3);
   Buffer buf2(kTestData, 6, 40);
-  uint8_t* data1 = buf1.data<uint8_t>();
-  uint8_t* data2 = buf2.data<uint8_t>();
+  uint8_t* data1 = buf1.data();
+  uint8_t* data2 = buf2.data();
   using std::swap;
   swap(buf1, buf2);
   EXPECT_EQ(buf1.size(), 6u);
   EXPECT_EQ(buf1.capacity(), 40u);
-  EXPECT_EQ(buf1.data<uint8_t>(), data2);
+  EXPECT_EQ(buf1.data(), data2);
   EXPECT_EQ(buf2.size(), 3u);
   EXPECT_EQ(buf2.capacity(), 3u);
-  EXPECT_EQ(buf2.data<uint8_t>(), data1);
+  EXPECT_EQ(buf2.data(), data1);
 }
 
 }  // namespace rtc