Add comprehensive memory barrier tests

src/tests/angle_end2end_tests.gni

@@ -84,6 +84,7 @@ angle_end2end_tests_sources = [
   "gl_tests/LinkAndRelinkTest.cpp",
   "gl_tests/MatrixTest.cpp",
   "gl_tests/MaxTextureSizeTest.cpp",
+  "gl_tests/MemoryBarrierTest.cpp",
   "gl_tests/MemoryObjectTest.cpp",
   "gl_tests/MemorySizeTest.cpp",
   "gl_tests/MipmapTest.cpp",

src/tests/gl_tests/ShaderStorageBufferTest.cpp

@@ -2539,6 +2539,7 @@ void main()
 
     // Verify the contents of the buffer.  It should have blue as the first index and green as the
     // second.
+    glMemoryBarrier(GL_BUFFER_UPDATE_BARRIER_BIT);
     GLColor *bufferContents = static_cast<GLColor *>(
         glMapBufferRange(GL_SHADER_STORAGE_BUFFER, 0, kBufferSize, GL_MAP_READ_BIT));
     EXPECT_GL_NO_ERROR();
@@ -2647,6 +2648,7 @@ void main()
     EXPECT_PIXEL_COLOR_EQ(0, 0, GLColor::blue);
 
     // Verify the contents of the buffer.
+    glMemoryBarrier(GL_BUFFER_UPDATE_BARRIER_BIT);
     uint32_t *bufferContents = static_cast<uint32_t *>(
         glMapBufferRange(GL_SHADER_STORAGE_BUFFER, 0, kBufferSize, GL_MAP_READ_BIT));
     EXPECT_GL_NO_ERROR();