Clean up some of the shader compilation code.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index f37c61a4808d9832879583c2321d05c2fdac9602..9ad26770273af8af34d82f96e39cf6abcd97c9cb 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -7051,14 +7051,17 @@ void GLES2DecoderImpl::DoShaderSource(
     GLuint client_id, GLsizei count, const char** data, const GLint* length) {
   std::string str;
   for (GLsizei ii = 0; ii < count; ++ii) {
-    str.append(data[ii]);
+    if (length && length[ii] > 0)
+      str.append(data[ii], length[ii]);
+    else
+      str.append(data[ii]);
   }
   Shader* shader = GetShaderInfoNotProgram(client_id, "glShaderSource");
   if (!shader) {
     return;
   }
   // Note: We don't actually call glShaderSource here. We wait until
-  // the call to glCompileShader.
+  // we actually compile the shader.
   shader->set_source(str);
 }