Added tests for NULL buffer data.

tests/angle_tests/BufferDataNULLTest.cpp

+#include "ANGLETest.h"
+
+class BufferDataNULLTest : public ANGLETest
+{
+protected:
+    BufferDataNULLTest()
+    {
+        setWindowWidth(1);
+        setWindowHeight(1);
+    }
+};
+
+TEST_F(BufferDataNULLTest, null_data)
+{
+    GLuint buf;
+    glGenBuffers(1, &buf);
+    ASSERT_NE(buf, 0U);
+
+    glBindBuffer(GL_ARRAY_BUFFER, buf);
+    EXPECT_GL_NO_ERROR();
+
+    const int numIterations = 128;
+    for (int i = 0; i < numIterations; ++i)
+    {
+        GLsizei bufferSize = sizeof(GLfloat) * (i + 1);
+        glBufferData(GL_ARRAY_BUFFER, bufferSize, NULL, GL_STATIC_DRAW);
+        EXPECT_GL_NO_ERROR();
+
+        for (int j = 0; j < bufferSize; j++)
+        {
+            for (int k = 0; k < bufferSize - j; k++)
+            {
+                glBufferSubData(GL_ARRAY_BUFFER, k, j, NULL);
+                EXPECT_GL_NO_ERROR();
+            }
+        }
+    }
+
+    glDeleteBuffers(1, &buf);
+    EXPECT_GL_NO_ERROR();
+}