diff --git a/dom/canvas/WebGLContext.cpp b/dom/canvas/WebGLContext.cpp
index b8639a7713..19de675203 100644
--- a/dom/canvas/WebGLContext.cpp
+++ b/dom/canvas/WebGLContext.cpp
@@ -88,19 +88,26 @@ using namespace mozilla::gl;
 using namespace mozilla::layers;
 
 WebGLContextOptions::WebGLContextOptions()
-    : alpha(true)
-    , depth(true)
-    , stencil(false)
-    , premultipliedAlpha(true)
-    , antialias(true)
-    , preserveDrawingBuffer(false)
-    , failIfMajorPerformanceCaveat(false)
 {
     // Set default alpha state based on preference.
     if (gfxPrefs::WebGLDefaultNoAlpha())
         alpha = false;
 }
 
+bool
+WebGLContextOptions::operator==(const WebGLContextOptions& r) const
+{
+    bool eq = true;
+    eq &= (alpha == r.alpha);
+    eq &= (depth == r.depth);
+    eq &= (stencil == r.stencil);
+    eq &= (premultipliedAlpha == r.premultipliedAlpha);
+    eq &= (antialias == r.antialias);
+    eq &= (preserveDrawingBuffer == r.preserveDrawingBuffer);
+    eq &= (failIfMajorPerformanceCaveat == r.failIfMajorPerformanceCaveat);
+    eq &= (powerPreference == r.powerPreference);
+    return eq;
+}
 
 /*static*/ const uint32_t WebGLContext::kMinMaxColorAttachments = 4;
 /*static*/ const uint32_t WebGLContext::kMinMaxDrawBuffers = 4;
@@ -375,6 +382,7 @@ WebGLContext::SetContextOptions(JSContext* cx, JS::Handle<JS::Value> options,
     newOpts.antialias = attributes.mAntialias;
     newOpts.preserveDrawingBuffer = attributes.mPreserveDrawingBuffer;
     newOpts.failIfMajorPerformanceCaveat = attributes.mFailIfMajorPerformanceCaveat;
+    newOpts.powerPreference = attributes.mPowerPreference;
 
     if (attributes.mAlpha.WasPassed())
         newOpts.alpha = attributes.mAlpha.Value();
@@ -393,7 +401,7 @@ WebGLContext::SetContextOptions(JSContext* cx, JS::Handle<JS::Value> options,
                newOpts.preserveDrawingBuffer ? 1 : 0);
 #endif
 
-    if (mOptionsFrozen && newOpts != mOptions) {
+    if (mOptionsFrozen && !(newOpts == mOptions)) {
         // Error if the options are already frozen, and the ones that were asked for
         // aren't the same as what they were originally.
         return NS_ERROR_FAILURE;
@@ -692,6 +700,16 @@ WebGLContext::CreateAndInitGL(bool forceEnabled,
         flags |= gl::CreateContextFlags::REQUIRE_COMPAT_PROFILE;
     }
 
+    switch (mOptions.powerPreference) {
+      case dom::WebGLPowerPreference::Low_power:
+        break;
+      case dom::WebGLPowerPreference::High_performance:
+      default:
+        // Default to high-performance if queried.
+        flags |= gl::CreateContextFlags::HIGH_POWER;
+        break;
+    }
+
     //////
 
     const bool useEGL = PR_GetEnv("MOZ_WEBGL_FORCE_EGL");
@@ -1377,6 +1395,7 @@ WebGLContext::GetContextAttributes(dom::Nullable<dom::WebGLContextAttributes>& r
     result.mPremultipliedAlpha = mOptions.premultipliedAlpha;
     result.mPreserveDrawingBuffer = mOptions.preserveDrawingBuffer;
     result.mFailIfMajorPerformanceCaveat = mOptions.failIfMajorPerformanceCaveat;
+    result.mPowerPreference = mOptions.powerPreference;
 }
 
 NS_IMETHODIMP
diff --git a/dom/canvas/WebGLContext.h b/dom/canvas/WebGLContext.h
index 8984b71366..6073da1754 100644
--- a/dom/canvas/WebGLContext.h
+++ b/dom/canvas/WebGLContext.h
@@ -137,30 +137,17 @@ void AssertUintParamCorrect(gl::GLContext* gl, GLenum pname, GLuint shadow);
 
 struct WebGLContextOptions
 {
-    // these are defaults
+    bool alpha = true;
+    bool depth = true;
+    bool stencil = false;
+    bool premultipliedAlpha = true;
+    bool antialias = true;
+    bool preserveDrawingBuffer = false;
+    bool failIfMajorPerformanceCaveat = false;
+    dom::WebGLPowerPreference powerPreference = dom::WebGLPowerPreference::Default;
+
     WebGLContextOptions();
-
-    bool operator==(const WebGLContextOptions& other) const {
-        return
-            alpha == other.alpha &&
-            depth == other.depth &&
-            stencil == other.stencil &&
-            premultipliedAlpha == other.premultipliedAlpha &&
-            antialias == other.antialias &&
-            preserveDrawingBuffer == other.preserveDrawingBuffer;
-    }
-
-    bool operator!=(const WebGLContextOptions& other) const {
-        return !operator==(other);
-    }
-
-    bool alpha;
-    bool depth;
-    bool stencil;
-    bool premultipliedAlpha;
-    bool antialias;
-    bool preserveDrawingBuffer;
-    bool failIfMajorPerformanceCaveat;
+    bool operator==(const WebGLContextOptions&) const;
 };
 
 // From WebGLContextUtils
diff --git a/dom/webidl/WebGLRenderingContext.webidl b/dom/webidl/WebGLRenderingContext.webidl
index 323d234219..8cff320b3f 100644
--- a/dom/webidl/WebGLRenderingContext.webidl
+++ b/dom/webidl/WebGLRenderingContext.webidl
@@ -32,6 +32,10 @@ typedef unrestricted float GLfloat;
 typedef unrestricted float GLclampf;
 typedef unsigned long long GLuint64EXT;
 
+// The power preference settings are documented in the WebGLContextAttributes
+// section of the specification.
+enum WebGLPowerPreference { "default", "low-power", "high-performance" };
+
 dictionary WebGLContextAttributes {
     // boolean alpha = true;
     // We deviate from the spec here.
@@ -43,6 +47,7 @@ dictionary WebGLContextAttributes {
     GLboolean premultipliedAlpha = true;
     GLboolean preserveDrawingBuffer = false;
     GLboolean failIfMajorPerformanceCaveat = false;
+    WebGLPowerPreference powerPreference = "default";
 };
 
 [Exposed=(Window,Worker),
diff --git a/gfx/gl/GLContextTypes.h b/gfx/gl/GLContextTypes.h
index de59acf491..b8ece51e88 100644
--- a/gfx/gl/GLContextTypes.h
+++ b/gfx/gl/GLContextTypes.h
@@ -45,7 +45,7 @@ struct GLFormats
     GLsizei samples;
 };
 
-enum class CreateContextFlags : int8_t {
+enum class CreateContextFlags : uint8_t {
     NONE = 0,
     REQUIRE_COMPAT_PROFILE = 1 << 0,
     // Force the use of hardware backed GL, don't allow software implementations.
@@ -56,6 +56,9 @@ enum class CreateContextFlags : int8_t {
     PREFER_ES3 = 1 << 3,
 
     NO_VALIDATION = 1 << 4,
+    //PREFER_ROBUSTNESS = 1 << 5, /* reserved for now */
+
+    HIGH_POWER = 1 << 6,
 };
 MOZ_MAKE_ENUM_CLASS_BITWISE_OPERATORS(CreateContextFlags)