Auto merge of #13553 - birtles:animvalues, r=Manishearth

Support creating StyleAnimationValue objects from Servo

These are the servo-side changes for [bug 1302949](https://bugzilla.mozilla.org/show_bug.cgi?id=1302949#c59). @Manishearth has already reviewed them there.

---
- [X] `./mach build -d` does not report any errors
- [X] `./mach test-tidy` does not report any errors
- [X] These changes fix [bug 1302949](https://bugzilla.mozilla.org/show_bug.cgi?id=1302949#c59)
- [X] These changes do not require tests because there are existing tests for this in mozilla-central

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---
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components/style/gecko/wrapper.rs

@@ -70,6 +70,16 @@ pub struct GeckoDeclarationBlock {
     pub immutable: AtomicBool,
 }
 
+impl PartialEq for GeckoDeclarationBlock {
+    fn eq(&self, other: &GeckoDeclarationBlock) -> bool {
+        match (&self.declarations, &other.declarations) {
+            (&None, &None) => true,
+            (&Some(ref s), &Some(ref other)) => *s.read() == *other.read(),
+            _ => false,
+        }
+    }
+}
+
 unsafe impl HasFFI for GeckoDeclarationBlock {
     type FFIType = bindings::ServoDeclarationBlock;
 }

components/style/gecko_bindings/bindings.rs

@@ -165,6 +165,7 @@ use gecko_bindings::structs::nsINode;
 use gecko_bindings::structs::nsIDocument;
 use gecko_bindings::structs::nsIPrincipal;
 use gecko_bindings::structs::nsIURI;
+use gecko_bindings::structs::nsString;
 use gecko_bindings::structs::RawGeckoNode;
 use gecko_bindings::structs::RawGeckoElement;
 use gecko_bindings::structs::RawGeckoDocument;
@@ -399,6 +400,11 @@ extern "C" {
                                               *const ::std::os::raw::c_char,
                                           aLength: u32) -> bool;
 }
+extern "C" {
+    pub fn Gecko_Utf8SliceToString(aString: *mut nsString,
+                                   aBuffer: *const u8,
+                                   aBufferLen: usize);
+}
 extern "C" {
     pub fn Gecko_FontFamilyList_Clear(aList: *mut FontFamilyList);
 }
@@ -847,6 +853,18 @@ extern "C" {
                                                  reference:
                                                      RawServoStyleSheetBorrowed);
 }
+extern "C" {
+    pub fn Servo_ParseProperty(property_bytes: *const u8,
+                               property_length: u32,
+                               value_bytes: *const u8,
+                               value_length: u32,
+                               base_bytes: *const u8,
+                               base_length: u32,
+                               base: *mut ThreadSafeURIHolder,
+                               referrer: *mut ThreadSafeURIHolder,
+                               principal: *mut ThreadSafePrincipalHolder)
+    -> ServoDeclarationBlockStrong;
+}
 extern "C" {
     pub fn Servo_ParseStyleAttribute(bytes: *const u8, length: u32,
                                      cache: *mut nsHTMLCSSStyleSheet)
@@ -860,6 +878,11 @@ extern "C" {
     pub fn Servo_DeclarationBlock_Release(declarations:
                                               ServoDeclarationBlockBorrowed);
 }
+extern "C" {
+    pub fn Servo_DeclarationBlock_Equals(a: ServoDeclarationBlockBorrowed,
+                                         b: ServoDeclarationBlockBorrowed)
+     -> bool;
+}
 extern "C" {
     pub fn Servo_DeclarationBlock_GetCache(declarations:
                                                ServoDeclarationBlockBorrowed)
@@ -929,6 +952,11 @@ extern "C" {
     pub fn Servo_RestyleSubtree(node: RawGeckoNodeBorrowed,
                                 set: RawServoStyleSetBorrowedMut);
 }
+extern "C" {
+    pub fn Servo_RestyleWithAddedDeclaration(declarations: ServoDeclarationBlockBorrowed,
+                                             previous_style: ServoComputedValuesBorrowed)
+     -> ServoComputedValuesStrong;
+}
 extern "C" {
     pub fn Servo_GetStyleFont(computed_values:
                                   ServoComputedValuesBorrowedOrNull)